TRANSPORTE DE GAMETAS, FERTILIZAÇÃO E SEGMENTAÇÃO -/- • _____OBJETIVO -/- O entendimento do desenvolvimento embrionário nos estágios iniciais, desde a deposição dos espermatozoides na fêmea, passando pela fertilização deste no ovócito e na formação do zigoto, é de suma importância para diferenciar especialistas em reprodução e manejo reprodutivo no mercado de trabalho e, também, durante a vida acadêmica. Compreender os processos que levam à formação do zigoto na fêmea é essencial para avaliar a capacidade reprodutiva dos animais e, mediante técnicas, (...) avaliar o trato reprodutivo da fêmea e o desenvolvimento do embrião até a formação do feto e, por fim, em um novo animal sadio na propriedade. Com esse trabalho, o estudante de veterinária ou zootecnia, que deseja se aprofundar na fisiologia da reprodução animal, identificará os mecanismos que são envolvidos no transporte dos gametas, bem como os processos que estes últimos devem completar para alcançar a fertilização e para desencadear as divisões iniciais do embrião. -/- • _____INTRODUÇÃO -/- A fertilização ou fecundação é o processo pelo qual os gametas masculino (espermatozoide) e feminino (ovócito) se fundem para gerar um novo indivíduo. Seu êxito depende da culminação adequada dos diferentes processos que devem sofrer os gametas durante sua maduração e percurso; do transporte oportuno destes no trato reprodutivo da fêmea, assim como de uma série de adaptações dos órgãos genitais internos da mãe. A segmentação refere-se às primeiras divisões celulares do embrião. -/- • _____TRANSPORTE DO OVÓCITO -/- O ovócito que é liberado na ovulação, e que se encontra coberto pelas células do cumulus (figura 1), é capturado pela fímbria do infundíbulo ao aderir aos cílios. Esse processo é altamente eficaz, inclusive em espécies onde os ovários possuem várias formações globosas, por exemplo nas porcas, onde os ovidutos capturam entre 95 e 100% dos ovócitos que são ovulados. As contrações das camadas musculares do oviduto e o movimento intenso dos cílios da mucosa faz com que as secreções fluam em direção ao útero, transportando assim o complexo cumulus-ovócito. Esse transporte é relativamente rápido até alcançar a junção da ampola com o istmo (que é considerado o local de fertilização do espermatozoide e ovócito) a partir do qual se torna lento. Devido a fêmea estar em estro, o processo está sob controle endócrino, isto é, controle hormonal através do estradiol. Nas fêmeas domésticas, ao contrário das mulheres, o transporte ao longo do oviduto é extremamente eficiente, pois os embriões passam para o útero sem dificuldade, de modo que gestações ectópicas (tubárias ou em cavidade) são quase inexistentes. A égua, frequentemente, retém por muito tempo os ovócitos não fertilizados no oviduto, provavelmente devido a não secreção de substâncias (como a prostaglandina E) que poderiam favorecer sua passagem, como se propõe que aconteça com os embriões. A figura 2 apresenta um ovócito com suas respectivas estruturas. Figura 1: ovócitos de uma vaca madurados in vitro. Nota-se as células do cumulus que os recobre. -/- Figura 2: estruturas do ovócito de uma ovelha que se encontra na etapa de ovócito secundário, depois da ovulação. Elaborado pelo autor. • _____TRANSPORTE ESPERMÁTICO -/- Para que os espermatozoides sejam capazes de fertilizar o ovócito, deverão sofrer uma série de mudanças bioquímicas e morfológicas ao longo de sua passagem pelo aparelho reprodutor tanto masculino como feminino. Uma vez produzidos na parede do túbulo seminífero, os espermatozoides são liberados em direção ao lúmen tubular e transportados passivamente para uma estrutura ramificada conhecida como rede testicular (rete testis). Dessa rede são conduzidos em direção ao epidídimo passando através de 10 a 20 ductos eferentes localizados no polo superior do testículo. O epidídimo é dividido em três seções denominadas cabeça, corpo e cauda; é constituído por um só ducto longo e tortuoso que continua com o canal deferente. Ao final desemboca nas ampolas seminais, no ducto ejaculatório e na uretra. As funções do epidídimo são as de maduração, transporte e armazenamento dos espermatozoides. O transporte através do epidídimo é lento, aproximadamente de 10 dias em touros, e segue sendo passivo. Os espermatozoides tomados da cabeça do epidídimo são ainda imaturos e incapazes de fertilizar, enquanto os armazenados na cauda são completamente maduros. Durante o trânsito pelo epidídimo os espermatozoides adquirem motilidade e o potencial para fertilizar, o acrossomo é remodelado e a gota citoplasmática migra para o flagelo e é liberada. Quando um macho ejacula com muita frequência, é possível observar espermatozoides com gota citoplasmática no sêmen, já que não há tempo suficiente para que completem sua maduração. Os espermatozoides são expulsados fora do organismo durante a cópula, na masturbação ou em emissões espontâneas. Na ejaculação, os espermatozoides que se encontram suspensos nos fluidos do testículo e do epidídimo, misturam-se ao chegar na uretra com as secreções das glândulas acessórias para formar o sêmen. Essas secreções denominadas plasma seminal, proporcionam substâncias para manter o metabolismo energético das células espermáticas, e integram suas membranas elementos que impedem uma capacitação prematura. Durante a cópula, o sêmen é depositado na vagina ou no útero, variando entre as espécies (tabela 1). Na monta natural, geralmente, o serviço ocorre no momento propício, já que está definido pela fase do ciclo estral em que a fêmea é receptiva ao macho. No entanto, na inseminação artificial, é o macho que deverá determinar o momento ideal, e para isso é importante considerar a vida média dos gametas, ao qual é muito curta no caso dos ovócitos (tabela 1). -/- Tabela 1: local de depósito do sêmen, volume da ejaculação e vida média dos gametas. Espécie Local de deposição Volume (ml) Velocidade de ejaculação Vida média do ovócito Vida média do espermatozoide Bovinos Intravaginal 2 1 – 3 seg 8 h 30 – 48 h Caninos Intravaginal 2 – 30 (10 média) 6 – 45 min 48 – 72 h 9 – 11 d Equinos Intrauterina 50 – 200 20 – 60 seg 6 – 8 h 72 – 120 h Humanos Intravaginal 3 - - 5 – 6 d Ovinos Intravaginal 1 1 – 2 seg 16 – 24 h 30 – 48 h Suínos Intrauterina 200 – 400 5 – 20 min 8 – 10 h 24 – 48 h Onde d = dias; h = horas. A vida fértil do ovócito é muito curta, portanto, o momento do serviço é de grande importância para obter altos índices de fertilização. -/- Independentemente do local em que os espermatozoides sejam depositados no aparelho reprodutor feminino, serão expostos às secreções genitais e sofrem uma série de mudanças em seu trajeto até o local de fertilização antes de penetrar no ovócito. Nas espécies em que o sêmen é depositado na parte cranial da vagina, uma parte do mesmo penetra através da cérvix, enquanto outra parte é eliminada do aparelho genital da fêmea, em pouco tempo, através do fluxo retrógrado. O meio vaginal não é adequado e imobiliza os espermatozoides em pouco tempo, pelo qual deverão entrar no útero onde o ambiente é mais propício. O transporte espermático na fêmea é o resultado da alta contratilidade, do movimento ciliar e o fluido do aparelho genital durante o estro, ao qual está sob controle endócrino e do sistema nervoso. Esse transporte é favorecido pelas características especiais do muco estral, cujas moléculas formam uma espécie de canais que facilitam a passagem dos espermatozoides. Pelo contrário, durante a fase lútea seu transporte é dificultado. Além do meio vaginal, a cérvix também atua como barreira natural para limitar a passagem dos espermatozoides, diminuindo assim a possibilidade de polispermia. Funciona, também, como um filtro que seleciona os espermatozoides aptos dos que não o são, uma vez que somente os primeiros possuem uma motilidade vigorosa que lhes permite passar pelo muco altamente hidratado. Na vaca a cérvix é considerada como um reservatório espermático. Quando atravessam a cérvix, os espermatozoides seguem sua deslocação tanto por movimento próprio como pelas contrações uterinas e tubárias. Nas espécies em que o local de depósito do sêmen do macho na fêmea é intrauterino, como equinos, a principal barreira que os espermatozoides enfrentam é a união ou junção útero-tubárica. A união entre o útero e o oviduto (istmo do oviduto) serve como reservatório funcional dos espermatozoides nas espécies domésticas. Poucos minutos depois da cópula, é possível encontrar alguns espermatozoides no oviduto, que é conhecido como fase de transporte rápido. No entanto, esses espermato-zoides não são os que participam do processo de fertilização e podem apresentar certas anormalidades. Existe um segundo tipo de transporte denominado fase sustentada, a qual consiste na migração prolongada dos espermatozoides em direção as partes mais craniais do aparelho genital feminino, que conduzem à colonização do reservatório funcional e na liberação gradual dos espermatozoides dos reservatórios espermáticos, incluindo este último. O reservatório do istmo fornece aos espermatozoides um ambiente propício, protegendo-os contra a fagocitose, prolongando assim a sua viabilidade. Aqui os esper-matozoides permanecem aderidos a superfície das células ciliadas do epitélio até a finalização de sua capacitação, depois da qual são liberados quando alteram seu padrão de motilidade flagelada, fenômeno conhecido como hipermotilidade, e migram em ondas em direção ao local da fertilização. Dos milhões de espermatozoides ejaculados, somente alguns milhares alcançarão o istmo do oviduto e um número sumamente pequeno será encontrado nas imediações do ovócito no momento da fertilização. -/- • _____CAPACITAÇÃO ESPERMÁTICA E REAÇÃO ACROSSÔMICA -/- A capacitação é um processo gradual e essencial para a fertilização. Os espermato-zoides devem passar por um dado tempo de “incubação” no aparelho genital da fêmea e sofrer uma série de mudanças antes de serem capazes de fecundar o ovócito. A capacita-ção dos espermatozoides começa quando eles entram em contato com as secreções do aparelho genital da fêmea e termina no istmo do oviduto. Durante esse percurso a superfície da cabeça do espermatozoide se modifica já que algumas moléculas como o colesterol são removidas da membrana plasmática, aumentando sua fluidez e alterando suas propriedades bioquímicas. Entre outras coisas, essa reorganização dos lipídios facilita a entrada de cálcio extracelular pelos canais iônicos e ocasiona a desestabilização da membrana, tornando-a mais fusogênica. Também são eliminados outros fatores (conhecidos genericamente como fatores descapacitantes) que expõem receptores membranais indispensáveis para a realização da união entre o espermatozoide e o ovócito durante a fertilização. Os espermatozoides capacitados apresentam um padrão de hipermotilidade e uma maior atividade metabólica, características que devem obter para que sejam capazes de penetrar as camadas do ovócito. A capacitação é necessária para que ocorra a reação acrossômica. A reação acrossomal ou acrossômica (RA) é um fenômeno de exocitose que é desencadeada pela ligação entre as proteínas e receptores localizados na membrana do espermatozoide e a zona pelúcida do ovócito (figura 3). Envolve a fusão da membrana plasmática do espermatozoide com a membrana externa de seu acrossomo; formando, assim, pequenas vesículas, cujo conteúdo de enzimas hidrolíticas, como a hialuronidase e a acrosina, é liberado em direção ao seu exterior, facilitando a penetração da zona pelúcida. A adesão do espermatozoide à zona pelúcida é específica da espécie e depende de glicoproteínas presentes na membrana dos ovócitos maduros; a cabeça do espermatozoide se une com essas glicoproteínas mediante receptores específicos e atravessam em direção oblíqua a zona pelúcida até chegar ao espaço perivitelino. Nos mamíferos, particularmente em roedores e nos humanos, algumas dessas glicoproteínas são conhecidas como ZP1, ZP2 e ZP3. Pensa-se que a união da membrana espermática a esta última é o que desencadeia a reação acrossomal. Posteriormente, as vilosidades do ovócito entram em contato com o espermatozoide e a membrana presente na secreção equatorial da cabeça do espermatozoide, que tem proteínas fusogênicas específicas, une-se a membrana plasmática do ovócito, fusionando-se e permitindo a entrada do núcleo espermático ao citoplasma (figura 4). A capacitação dos espermatozoides é fundamental para o êxito da fertilização, uma vez que apenas os aptos estarão perfeitos e íntegros para que a união e percepção das glicoproteínas presentes nos mesmos possam ocorrer de forma ideal para a penetração deste no ovócito, fertilizá-lo e formar um zigoto. Figura 3: estrutura do espermatozoide. Nota: a membrana é acrossomal e não acrossonal. Elaborado pelo autor. -/- Figura 4: eventos que ocorrem durante a fertilização. A – depois de passar através das células do cumulus, o espermatozoide entra em contato com a zona pelúcida, onde receptores da membrana plasmática reconhecem as proteínas da zona pelúcida; B – é desencadeada, então, a reação acrossomal; C – para que o espermatozoide penetre na zona pelúcida; D – ao atravessar a zona pelúcida e entrar no espaço perivitelino, a cabeça do espermatozoide entra em contato com a membrana vitelina; ambas membranas se fusionam graças ao reconhecimento de proteínas fusogênicas que estão no segmento equatorial. E – ocorre, então, que o núcleo do espermatozoide penetra no citoplasma do ovócito; uma das consequências da fusão da membrana com a cabeça do espermatozoide é a reação cortical, em que os grânulos corticais do ovócito liberam seu conteúdo em direção ao espaço perivitelino, o que resulta na alteração da estrutura da zona pelúcida e da membrana vitelina para bloquear a polispermia. Elaborado pelo autor. • _____CONSEQUÊNCIAS DA PENETRAÇÃO -/- Bloqueio da polispermia -/- A fusão das membranas dos gametas durante a penetração permite a entrada da fosfolipase C zeta (PLCζ) – fator solúvel que provém do espermatozoide – que desencadeia liberação e oscilações de Ca2+ no retículo endoplasmático. Isso, por sua vez, provoca a migração e fusão dos grânulos corticais, com a consequente liberação de enzimas, que mudam tanto a estrutura da zona pelúcida (por exemplo a inativação de ZP3), como a da membrana vitelina. Desse modo, impede-se que outros espermatozoides as penetrem, evitando assim a polispermia (figura 5). -/- Figura 5: os grânulos corticais que encontram-se na periferia do citoplasma, debaixo da superfície da membrana do ovócito, migram e fusionam-se sobre a mesma, liberando seu conteúdo no espaço perivitelino imediatamente depois da penetração do espermatozoide. A – como conse-quência, tanto a membrana vitelina como a zona pelúcida são modificadas, impedindo a entrada de mais espermatozoides, o que evita a polispermia. B – o ovócito retoma, então, sua segunda divisão meiótica, que ocasiona a expulsão do segundo corpúsculo polar, e na formação dos pronúcleos feminino e masculino. C – continuando, os pronúcleos migram, suas membranas se dissolvem e os cromossomos de ambos se condensam e se unem. Completa-se, assim, a singamia e forma-se, então, o zigoto. Elaborado pelo autor baseado nos livros de embriologia e fisiologia da reprodução conforme vida bibliografia. -/- Ativação do ovócito e formação de pronúcleos -/- Na maioria das fêmeas domésticas, com exceção da cadela, o ovócito encontra-se suspenso na metáfase II da segunda meiose no momento da ovulação. A entrada da PLCζ do espermatozoide no citoplasma do ovócito, e a consequente liberação de Ca2+, faz com que o ovócito se ative, terminando a segunda divisão meiótica e expulse o segundo corpo polar. Posteriormente, o material nuclear do ovócito se reorganiza para formar o pronú-cleo feminino. Entretanto, a membrana nuclear do espermatozoide se dissolve, a cromatina descondensa-se, as protaminas são substituídas por histonas, e se forma uma nova membrana nuclear, dando lugar ao pronúcleo masculino. -/- Singamia -/- Uma vez que os pronúcleos feminino e masculino são formados, migram para o centro do ovócito, aproximam-se, suas membranas se dispersam e os cromossomos paternos e maternos se associam, com o qual recupera a condição diploide e dá origem ao zigoto (figura 5). -/- • _____DESENVOLVIMENTO EMBRIONÁRIO -/- Poucas horas após a fertilização ocorre a primeira divisão do zigoto em duas, depois em 4, 8, 16 e 32 células, denominadas blastômeros. Essas divisões mitóticas são conhecidas como divisões de segmentação ou clivagem (figura 6), uma vez que são realizadas sem aumento do citoplasma, de modo que com cada divisão os blastômeros se tornam menores. A partir das 16 células o embrião se chama mórula, e é visto como uma massa celular compacta. A compactação deve-se a informação de proteínas de ligação entre os blastômeros. O embrião acumula líquido em seu interior, formando uma cavidade denominada blastocele. Esse processo é conhecido como blastulação; o embrião, assim, passa a ser chamado de blastocisto. Nessa etapa é possível diferenciar duas populações de células embrionárias: a massa celular interna, embrioblasto ou botão embrionário (que dará origem ao embrião), e a massa celular externa, células superficiais ou trofoblasto, do qual se originam a maioria das membranas fetais. Ao continuar a multiplicação das células e a acumulação de líquido, o blastocisto aumenta de tamanho, convertendo-se em blastocisto expandido. A zona pelúcida torna-se mais fina e, finalmente, o embrião eclode; isto é, o embrião é liberado da zona pelúcida. -/- • _____FERTILIZAÇÕES ATÍPICAS -/- Polispermia -/- É a penetração de dois ou mais espermatozoides no óvulo. Esta condição é letal nos mamíferos, já que o número cromossômico desse zigoto é maior que 2n, o envelheci-mento do ovócito da porca, como consequência do serviço tardio, favorece a apresentação da polispermia, por isso, é comum ver números de nascimentos de média de 10 a 12 leitões por parição nessa espécie. Nas aves, no entanto, a penetração de mais de um espermatozoide é normal, embora apenas um pronúcleo masculino se formará, fundindo-se com o feminino. -/- Figura 6: etapas do processo de segmentação/clivagem. Fonte: aula de reprodução da professora Domenica Palomaris, UFT. -/- Ginogênese -/- É o desenvolvimento de um embrião a partir de um óvulo normal fecundado por um espermatozoide, mas sem a fusão dos cromossomos masculinos com os da fêmea. A função do espermatozoide, nesse caso, é a de ativação do ovócito para que este inicie seu desenvolvimento, mas não há fusão com o núcleo do espermatozoide. Ocorre em plantas, em nematódeos e em algumas espécies de peixes, por exemplo a Poecilia formosa, espécie em que os ovócitos das fêmeas são ativados por machos de outra espécie relacio-nada. -/- Partenogênese -/- Consiste no desenvolvimento do embrião sem a participação do espermatozoide. Ocorre em alguns insetos, o zangão, por exemplo, é partenogenético. Também pode apresentar-se em perus, cujos embriões são machos e, geralmente, morrem antes da eclosão. -/- • _____GÊMEOS -/- Existem dois tipos de gêmeos: idênticos ou monozigóticos e os não idênticos ou dizigóticos. -/- Idênticos ou monozigóticos -/- Originam-se do mesmo zigoto, sendo assim, possuem o mesmo genótipo e um fenótipo similar e, portanto, são do mesmo sexo. Em laboratório é possível gerá-los ao seccionar uma mórula em duas ou mais partes, por meio de um micromanipulador. Uma vez que possuem o mesmo genótipo, os produtos resultantes são clones. -/- Não idênticos ou dizigóticos -/- Provêm da fertilização de dois óvulos distintos por espermatozoides diferentes. Possuem, portanto, genótipos e fenótipos diferentes, e podem ser de sexo diferente. -/- REFERÊNCIAS BIBLIOGRÁFICAS -/- ALBERTS, Bruce et al. Biologia molecular da célula. Artmed Editora, 2010. AUSTIN, Colin Russell; SHORT, Roger Valentine. Reproduction in Mammals, Book I: Germ Cells and Fertilization. 1982. BEARDEN, Henry Joe et al. Reproducción animal aplicada. México: Manual Moderno, 1982. BOSCH, P.; WRIGHT JR, R. W. The oviductal sperm reservoir in domestic mammals. Archivos de medicina veterinaria, v. 37, n. 2, p. 95-105, 2005. CAPALLEJAS, Roberto Brito; RODRÍGUEZ, Lourdes Tagle. Fisiología de la reproducción animal: con elementos de biotecnología. Editorial Félix Varela, 2010. CROXATTO, Horacio B. Physiology of gamete and embryo transport through the fallopian tube. Reproductive biomedicine online, v. 4, n. 2, p. 160-169, 2002. CUPPS, Perry T. (Ed.). Reproduction in domestic animals. Elsevier, 1991. DIEDRICH, Smidt et al. Endocrinología y Fisiología de la Reproducción de los Animales Zootécnicos. 1972. DUKES, Henry Hugh; SWENSON, Melvin J.; REECE, William O. Dukes fisiologia dos animais domésticos. Editora Guanabara Koogan, 1996. FERREIRA, A. de M. Reprodução da fêmea bovina: fisiologia aplicada e problemas mais comuns (causas e tratamentos). Juiz de Fora: Minas Gerais–Brasil, p. 422, 2010. HAFEZ, Elsayed Saad Eldin; HAFEZ, Bahaa. Reprodução animal. São Paulo: Manole, 2004. HUNTER, Ronald Henry Fraser. The Fallopian tubes in domestic mammals: how vital is their physiological activity?. Reproduction Nutrition Development, v. 45, n. 3, p. 281-290, 2005. HUNTER, R. H. F.; RODRIGUEZ‐MARTINEZ, H. Capacitation of mammalian spermatozoa in vivo, with a specific focus on events in the Fallopian tubes. Molecular Reproduction and Development: Incorporating Gamete Research, v. 67, n. 2, p. 243-250, 2004. GALINA, Carlos; VALENCIA, Javier. Reproducción de los animales domésticos. 2006. HOPPER, Richard M. (Ed.). Bovine reproduction. John Wiley & Sons, 2014. HYTTEL, Poul; SINOWATZ, Fred; VEJLSTED, Morten. Embriologia veterinária. Elsevier Brasil, 2012. KÖLLE, Sabine; REESE, Sven; KUMMER, Wolfgang. New aspects of gamete transport, fertilization, and embryonic development in the oviduct gained by means of live cell imaging. Theriogenology, v. 73, n. 6, p. 786-795, 2010. MCKINNON, Angus O. et al. (Ed.). Equine reproduction. John Wiley & Sons, 2011. OLIVERA, Martha et al. El espermatozoide, desde la eyaculación hasta la fertilización. Revista Colombiana de Ciencias Pecuarias, v. 19, n. 4, p. 426-436, 2006. PLANT, Tony M.; ZELEZNIK, Anthony J. (Ed.). Knobil and Neill's physiology of reproduction. New York: Academic Press, 2014. RODRIGUEZ-MARTINEZ, Heriberto. Role of the oviduct in sperm capacitation. Theriogenology, v. 68, p. S138-S146, 2007. SAAVEDRA LEOS, María Dolores. Estudio de la composición de los gránulos corticales y del oolema de ovocitos porcinos y bovinos madurados y fecundados in vitro. Proyecto de investigación:, 2010. SENGER, Phillip L. et al. Pathways to pregnancy and parturition. Current Conceptions, Inc, 2004. SUAREZ, Susan S. The oviductal sperm reservoir in mammals: mechanisms of formation. Biology of Reproduction, v. 58, n. 5, p. 1105-1107, 1998. VALENCIA MÉNDEZ, Javier de J. Fisiología de la reproducción porcina. 1986. -/- FIXAÇÃO DO ASSUNTO -/- 1. Defina e diferencie fertilização e segmentação. -/- 2. Disserte sobre o transporte do ovócito. Por que no istmo o transporte do ovócito se torna lento? -/- 3. Fale sobre a eficiência do transporte do gameta no trato genital da fêmea e sobre a retenção de ovócitos pela égua. -/- 4. Defina as células do cumulus e explique seu papel sobre o ovócito. -/- 5. Quais as estruturas que compõem o ovócito? Qual a função de cada uma? -/- 6. Todos os ovócitos das fêmeas domésticas são iguais? Justifique. -/- 7. Disserte sobre o papel dos hormônios e das secreções sobre o transporte do ovócito no trato genital da fêmea. -/- 8. Disserte sobre o transporte do espermatozoide. Por que há transporte rápido e lento dos espermatozoides? -/- 9. Fale sobre o local de deposição do sêmen nas espécies domésticas e como esse influen-cia na eficiência da reprodução. -/- 10. Por que a vida média do espermatozoide canino é maior que as outras espécies? -/- 11. Quais as mudanças que os espermatozoides precisam sofrer para conseguir êxito na fertilização e por quê? -/- 12. Defina fase de transporte rápido, fase sustentada e hipermotilidade. Qual a importân-cia de cada um? -/- 13. Como ocorre a reação acrossômica? -/- 14. O que é polispermia e como ocorre seu bloqueio? 15. Como ocorre a ativação do ovócito e como se formam os pronúcleos? -/- 16. O que é e qual a importância da singamia? -/- 17. Disserte sobre as divisões de segmentação e qual a importância destas para o êxito da reprodução. -/- 18. Defina e diferencia mórula e blastocisto. -/- 19. Defina e diferencie ginogênese e partenogênese. -/- 20. Qual o papel endócrino e quais hormônios e enzimas atuam sobre o transporte de gametas, sobre a fertilização e sobre a segmentação? (shrink)

One of the most influential and controversial schools of 20th century Thomism—especially in North America—is the “River Forest School” or “River Forest Thomism”. And one of the most influential and controversial theses associated with that school is the thesis that metaphysics cannot be established as a distinct and autonomous science unless one has already proven the existence of a positively immaterial being. The purpose of this paper is to show that River Forest Thomism cannot and should not be reduced to (...) that controversial thesis. As such, rejection of the thesis cannot and should not constitute a rejection of the school. Indeed, as soon as we understand what River Forest Thomism was really about, it will become clear that all Thomists should be River Forest Thomists. (shrink)

We provide a new interpretation of Zeno’s Paradox of Measure that begins by giving a substantive account, drawn from Aristotle’s text, of the fact that points lack magnitude. The main elements of this account are (1) the Axiom of Archimedes which states that there are no infinitesimal magnitudes, and (2) the principle that all assignments of magnitude, or lack thereof, must be grounded in the magnitude of line segments, the primary objects to which the notion of linear magnitude applies. Armed (...) with this account, we are ineluctably driven to introduce a highly constructive notion of (outer) measure based exclusively on the total magnitude of potentially infinite collections of line segments. The Paradox of Measure then consists in the proof that every finite or potentially infinite collection of points lacks magnitude with respect to this notion of measure. We observe that the Paradox of Measure, thus understood, troubled analysts into the 1880’s, despite their knowledge that the linear continuum is uncountable. The Paradox was ultimately resolved by Borel in his thesis of 1893, as a corollary to his celebrated result that every countable open cover of a closed line segment has a finite sub-cover, a result he later called the “First Fundamental Theorem of Measure Theory.” This achievement of Borel has not been sufficiently appreciated. We conclude with a metamathematical analysis of the resolution of the paradox made possible by recent results in reverse mathematics. (shrink)

The sense of form that provides the modern poet with a unique experience of the literary object has been crucial to various attempts to compare poetry to other cultural activities. In maintaining similar conceptions of the relationship between poetry and painting, Arthur Rimbaud and W. C. Williams establish a common basis for interpreting their creative work. And yet their poetry is more crucially concerned with the sudden emergence of visible "worlds" containing verbal objects that integrate a new kind of literary (...) text. This paper discusses the emergence of "aesthetic worlds" in the work of both poets and then examines how a common concern with Baroque form unites them in the phenomenological task of overcoming Cartesian dualism. (shrink)

Many will readily acknowledge there being rights of humans which trump the rights of states. Thus, these rights are aptly labeled ‘Human Rights,’ by which we may measure and admonish state-conduct. However, in contemporary Human Rights discourse, there is an emerging strand of thought in the academy that is Anti-Human Rights. To understand the foundations of Anti-Human Rights discourse, and to address the arguments that have been put forth, I analyze and incorporate the works of John O. Nelson, Raymond Geuss, (...) Wendy Brown, and Slavoj Žižek. Based on the same, I argue that the core arguments to these assertions are unpersuasive. I attempt at viewing Human Rights justification in different terms, and, to argue for the legitimacy of Human Rights while abandoning the search for justifications in nature, U.S. Foreign Policy, or Neo-Marxist views. (shrink)

Many philosophers and scientists claim that there is a ‘hard problem of consciousness’, that qualia, phenomenology, or subjective experience cannot be fully understood with reductive methods of neuroscience and psychology, and that there is a fact of the matter as to ‘what it is like’ to be conscious and which entities are conscious (Chalmers, 1995). Eliminativism and related views such as illusionism argue against this; they claim that consciousness does not exist in the ways implied by everyday or scholarly language. (...) However, this debate has largely consisted of each side jousting analogies and intuitions against the other. Both sides remain unconvinced. To break through this impasse, I present _consciousness semanticism_, a novel eliminativist theory that sidesteps analogy and intuition. Instead, it is based on a direct, formal argument drawing from the tension between the vague semantics in definitions of consciousness such as ‘what it is like’ to be an entity (Nagel, 1975) and the precise meaning implied by questions such as, ‘Is this entity conscious?’ I argue that semanticism naturally extends to erode realist notions of other philosophical concepts, such as morality and free will. Formal argumentation from precise semantics exposes these as pseudo-problems and removes their apparent mysteriousness and intractability. (shrink)

In their Why Machines Will Never Rule the World, Landgrebe and Smith (2023) argue that it is impossible for artificial general intelligence (AGI) to succeed, on the grounds that it is impossible to perfectly model or emulate the “complex” “human neurocognitive system”. However, they do not show that it is logically impossible; they only show that it is practically impossible using current mathematical techniques. Nor do they prove that there could not be any other kinds of theories than those in (...) current use. Even if perfect theories were impossible or unlikely, perfection may not be needed and may even be unhelpful. (shrink)

We must, therefore, make a study of mechanism; but some introduction is advisable, for cybernetics treats the subject from a new, and therefore unusual, ...

How do we determine whether individuals accept the actual consistency of a political argument instead of just its rhetorical good looks? This article answers this question by proposing an interpretation of political argument within the constraints of political liberalism. It utilises modern developments in the philosophy of logic and language to reclaim ‘meaningless nonsense’ from use as a partisan war cry and to build up political argument as something more than a power struggle between competing conceptions of the good. Standard (...) solutions for ‘clarifying’ meaning through descriptive definition encounter difficulties with the biases of status quo idioms (long noted by theorists like William Connolly and Quentin Skinner), as well as partisan translations and circularity. Collectively called linguistic gerrymandering, these difficulties threaten political liberalism’s underlying coherency. The proposed interpretation of political argument overcomes this with a new brand of conceptual analysis that can falsifiably determine whether rhetoric has hijacked political argument. (shrink)

The harmonious free play of the imagination and understanding is at the heart of Kant’s account of beauty in the Critique of the Power of Judgement, but interpreters have long struggled to determine what Kant means when he claims the faculties are in a state of free play. In this article, I develop an interpretation of the free play of the faculties in terms of the freedom of attention. By appealing to the different way that we attend to objects in (...) aesthetic experience, we can explain how the faculties are free, even when the subject already possesses a concept of the object and is bound to the determinate form of the object in perception. (shrink)

What methodological approaches do research programs use to investigate the world? Elisabeth Lloyd’s Logic of Research Questions (LRQ) characterizes such approaches in terms of the questions that the researchers ask and causal factors they consider. She uses the Logic of Research Questions Framework to criticize adaptationist programs in evolutionary biology for dogmatically assuming selection explanations of the traits of organisms. I argue that Lloyd’s general criticism of methodological adaptationism is an artefact of the impoverished LRQ. My Ordered Factors Proposal extends (...) the LRQ to characterize approaches with sequences of questions and factors. I highlight the importance that ordering one’s investigation plays in approaches at the level of adaptationism by analyzing two research programs in community ecology: competitionists and neutralists. Competitionists and neutralists take opposed starting points and use explanatory and developmental heuristics to consider more factors in due time. On the Ordered Factors Proposal, these approaches are not only the ecological factors they are open to considering but also the order in which they will consider them. My disagreement with Lloyd’s over how to characterize methodological approaches reflects different views about methodological monism and pluralism. (shrink)

Gerald Gaus argued in his 1996 book Justificatory Liberalism that proponents of public reason liberalism should attempt to ground their position in a specific epistemology. Critics of public reason liberalism such as David Enoch have also argued that public reason liberals need to elucidate their epistemic claims. Surprisingly, few public reason liberals have taken up Gaus and Enoch on their challenge. This paper will interact with the epistemological position undergirding the public justification principle, access internalism, arguing that it fails. In (...) its place, I put forward and defend proper functionalism as the better grounding epistemology, and then defend the new theory from possible objections. The result will be a synthesis of Nicholas Wolterstorff’s version of liberalism and an externalist version of convergence public reason liberalism. (shrink)

Although the Evans argument against vague identity has been much discussed, proposah for blocking it have not so far satisfied general conditions which any solution ought to meet. Moreover, the relation between ontically vague identity and ontic vagueness more generally has not yet been satisfactorily addressed. I advocate a way of resisting the Evans argument which satisfies the conditions. To show how this approach can vindicate particular cases of ontically vague identity, I develop a framework for describing ontic vagueness in (...) general in terms of multiple actualities. This provides aprìncipled approach to ontically vague identity which is unaffected by the Evans argument. (shrink)

This précis summarizes the main topics, arguments and conclusions of the book. Many interesting arguments and critiques have, of course, been omitted in order to make this summary appropriately brief.

L’érosion actuelle de la confiance du public envers les campagnes de vaccination et les décisions de politiques publiques qui y sont associées, aggravée par des scandales comme ceux relatifs à la pandémie H1N1 et l’utilisation du Tamiflu™, risque de diminuer de façon significative l’efficacité de ces interventions importantes pour la santé publique. Un manque de confiance de la population envers les acteurs de santé publique peut conduire à une méfiance accrue face aux interventions, pouvant ainsi compromettre l’atteinte des objectifs recherchés (...) par une intervention spécifique et, conséquemment, avoir un impact important sur les bénéfices attendus pour la population visée par cette intervention. Dans la production des avis d’experts, les membres des comités consultatifs d’experts en immunisation (CCEI) peuvent avoir une influence importante sur la prise de décision publique, notamment, sur la sélection par les décideurs de santé publique de vaccins en particulier et la façon dont les campagnes de vaccination seront déployées. En contrepartie de cette influence sur les décisions publiques, une indépendance et une transparence sont attendues de leur part puisque des mécanismes de divulgation et de gestion de conflits d’intérêts (CI) imparfaits peuvent affecter négativement la confiance du public à l’égard de telles décisions. Il apparaît donc important de s’assurer que des mécanismes de gestion des CI, transparents et robustes, existent pour ces comités. Dans cette étude, les avis ou rapports d’évaluation de la pertinence de la vaccination préparés par un CCEI au Québec ont été examinés pour quatre types de maladies évitables par la vaccination (infections invasives à méningocoques et à pneumocoques, coqueluche et virus du papillome humain). Le but était de : 1) identifier les CI divulgués par les membres du CCEI dans leurs rapports comparativement à ceux déclarés dans leurs publications scientifiques pour ces mêmes infections ; 2) analyser la nature des CI (réel, potentiel, apparent, personnel, financier, institutionnel, etc.) et l’impact potentiel (risque) sur la prise de décision impartiale et sur la confiance du public ; et 3) évaluer les mécanismes de gestion de CI actuellement utilisés par ce CCEI. Les résultats de cette étude montrent que très peu de rapports du CCEI contiennent une section sur les CI par rapport à la pléthore divulguée dans les publications scientifiques publiées par les membres du CCEI. De plus, les CI divulgués dans les rapports fréquemment ne correspondent pas à ceux décrits dans les publications scientifiques. Il serait donc important d’introduire des mesures visant à accroître la transparence des experts en immunisation et d’améliorer les mécanismes de divulgation et de gestion des CI afin de veiller à ce que la confiance du public envers les décideurs en santé publique soit maintenue et améliorée. (shrink)

Suppose that an altruistic agent who is uncertain between evidential and causal decision theory finds herself in a situation where these theories give conflicting verdicts. We argue that even if she has significantly higher credence in CDT, she should nevertheless act in accordance with EDT. First, we claim that the appropriate response to normative uncertainty is to hedge one's bets. That is, if the stakes are much higher on one theory than another, and the credences you assign to each of (...) these theories are not very different, then it is appropriate to choose the option that performs best on the high-stakes theory. Second, we show that, given the assumption of altruism, the existence of correlated decision makers will increase the stakes for EDT but leave the stakes for CDT unaffected. Together these two claims imply that whenever there are sufficiently many correlated agents, the appropriate response is to act in accordance with EDT. (shrink)

This article focuses on the positive reasons for adopting epiphenomenalism. Some objections that have been answered in more detail in my other work receive some response here, but the main point is to see why epiphenomenalism is an attractive view for those with a generally naturalistic outlook. It distinguishes qualitative events from propositional states and explains why their treatment must be different. The view that our words must 'express our thoughts' is critically examined.

Lewis (1973) gave a short argument against conditional excluded middle, based on his treatment of ‘might’ counterfactuals. Bennett (2003), with much of the recent literature, gives an alternative take on ‘might’ counterfactuals. But Bennett claims the might-argument against CEM still goes through. This turns on a specific claim I call Bennett’s Hypothesis. I argue that independently of issues to do with the proper analysis of might-counterfactuals, Bennett’s Hypothesis is inconsistent with CEM. But Bennett’s Hypothesis is independently objectionable, so we should (...) resolve this tension by dropping the Hypothesis, not by dropping CEM. (shrink)

Revisionary theories of logic or truth require revisionary theories of mind. This essay outlines nonclassically based theories of rational belief, desire, and decision making, singling out the supervaluational family for special attention. To see these nonclassical theories of mind in action, this essay examines a debate between David Lewis and Derek Parfit over what matters in survival. Lewis argued that indeterminacy in personal identity allows caring about psychological connectedness and caring about personal identity to amount to the same thing. The (...) essay argues that Lewis's treatment of two of Parfit's puzzle cases—degreed survival and fission—presuppose different nonclassical treatments of belief and desire. (shrink)

An overview of the ancient philosophers and their philosophical system (divided into the fields of logic, physics, and ethics) comprising the living, organic, enduring, and evolving body of interrelated ideas identifiable as the Stoic perspective.

The question of the cognitive role of fictionality is this: what is the correct cognitive attitude to take to p, when it is fictional that p? We began by considering one answer to this question, implicit in the work of Kendall Walton, that the correct response to a fictional proposition is to imagine that proposition. However, this approach is silent in cases of fictional incompleteness, where neither p nor its negation are fictional. We argue that that Waltonians should embrace a (...) pluralistic account of the cognitive role of fictional incompleteness: in some cases of fictional incompleteness, we are permitted to resolve the incompleteness during our engagement with the target fiction, and in other cases, we are obliged not to resolve the incompleteness. But though pluralism is accommodated by Walton’s wider account of fictionality, it puts tension on his motivating idea that fictionality stands to the imagination as truth stands to belief. And so we develop a rival conception of the cognitive role of fictionality that is built around a different analogy: on this evidentialist approach, (known) fictionality stands to the imagination as evidence stands to credence. (shrink)

For the purposes of this enquiry—an account of what Equiano’sa modernity was, and which particular historical ‘demarcations’ of modernity provided for an enslaved man to achieve freedom through great fortune and great cunning, I will assume a definition of ‘modernity’ as defined by Kathleen Wilson: “. . . not one moment or age, but a set of relations that are constantly being made and unmade, contested and reconfigured, that nonetheless produce among their contemporaneous witnesses the conviction of historical difference.” By (...) adopting this definition, modernity in the times of Equiano refers to, “the cultural practices and representations that produced certain kinds of subjects and objects of knowledge, upheld widely-shared notions of space and time, or facilitated the formation of cultural identities that resulted in pluralities and contradictions as well as unities and coherences,” which provided for a slave to acquire freedom amidst eighteenth-century imperialism, slave-trade, and emerging abolitionist sentiments within bourgeois culture. (shrink)

Neutral Theory is controversial in ecology. Ecologists and philosophers have diagnosed the source of the controversy as: its false assumption that individuals in different species within the same trophic level are ecologically equivalent, its conflict with Competition Theory and the adaptation of species, its role as a null hypothesis, and as a Lakatosian research programme. In this paper, I show why we should instead understand the conflict at the level of research programs which involve more than theory. The Neutralist and (...) Competitionist research programs borrow and construct theories, models, and experiments for various aims and given their home ecological systems. I present a holistic and pragmatic view of the controversy that foregrounds the interrelation between many kinds of practices and decisions in ecological research. (shrink)

This article examines one of the sources of David Benatar’s anti-natalism. This is the view that ‘all procreation is [morally] wrong.’ (Benatar and Wasserman, 2015:12) One of its sources is the claim that each of our lives is objectively bad, hence bad whether we think so or not. The question I will pose is whether the constraints of metaphysical naturalism allow for an objective devaluation of human life sufficiently negative to justify anti-natalism. My thesis is that metaphysical naturalism does not (...) have the resources to support such a negative evaluation. Metaphysical naturalism is the view that causal reality is exhausted by nature, the space-time system and its contents. The gist of my argument is that the ideal standards relative to which our lives are supposed to be axiologically substandard cannot be merely subjective expressions of our desires and aversions; they must be (i) objectively binding standards that are (ii) objectively possible in the sense of concretely realizable. The realizability condition, however, cannot be satisfied on metaphysical naturalism; ergo, failure to meet these ideal standards cannot show that our lives are objectively bad. (shrink)

Probabilistic support is not transitive. There are cases in which x probabilistically supports y , i.e., Pr( y | x ) > Pr( y ), y , in turn, probabilistically supports z , and yet it is not the case that x probabilistically supports z . Tomoji Shogenji, though, establishes a condition for transitivity in probabilistic support, that is, a condition such that, for any x , y , and z , if Pr( y | x ) > Pr( y (...) ), Pr( z | y ) > Pr( z ), and the condition in question is satisfied, then Pr( z | x ) > Pr( z ). I argue for a second and weaker condition for transitivity in probabilistic support. This condition, or the principle involving it, makes it easier (than does the condition Shogenji provides) to establish claims of probabilistic support, and has the potential to play an important role in at least some areas of philosophy. (shrink)

Drawing on a passage from Ramsey's Truth and Probability, we formulate a simple, plausible constraint on evaluating the accuracy of credences: the Calibration Test. We show that any additive, continuous accuracy measure that passes the Calibration Test will be strictly proper. Strictly proper accuracy measures are known to support the touchstone results of accuracy-first epistemology, for example vindications of probabilism and conditionalization. We show that our use of Calibration is an improvement on previous such appeals by showing how it answers (...) or sidesteps problems that have been raised for previous work in this area. (shrink)

We argue elsewhere that explanatoriness is evidentially irrelevant . Let H be some hypothesis, O some observation, and E the proposition that H would explain O if H and O were true. Then O screens-off E from H: Pr = Pr. This thesis, hereafter “SOT” , is defended by appeal to a representative case. The case concerns smoking and lung cancer. McCain and Poston grant that SOT holds in cases, like our case concerning smoking and lung cancer, that involve frequency (...) data. However, McCain and Poston contend that there is a wider sense of evidential relevance—wider than the sense at play in SOT—on which explanatoriness is evidentially relevant even in cases involving frequency data. This is their main point, but they also contend that SOT does not hold in certain cases not involving frequency data. We reply to each of these points and conclude with some general remarks on screening-off as a test of evidential relevance. (shrink)

No existing conditional semantics captures the dual role of 'if' in embedded interrogatives — 'X wonders if p' — and conditionals. This paper presses the importance and extent of this challenge, linking it to cross-linguistic patterns and other phenomena involving conditionals. Among these other phenomena are conditionals with multiple 'if'-clauses in the antecedent — 'if p and if q, then r' — and relevance conditionals — 'if you are hungry, there is food in the cupboard'. Both phenomena are shown to (...) be problematic for existing analyses. Surprisingly, the decomposition of conditionals needed to capture the link with interrogatives provides a new analysis that captures all three phenomena. The model-theoretic semantics offered here relies on a dynamic conception of meaning and compositionality, a feature discussed throughout. (shrink)

What is the relation between meaning and use? This chapter first defends a non-reductionist understanding of Wittgenstein’s suggestion that ‘the meaning of a word is its use in the language’; facts about meaning cannot be reduced to, or explained in terms of, facts about use, characterized non-semantically. Nonetheless, it is contended, facts about meaning do supervene on non-semantic facts about use. That supervenience thesis is suggested by comments of Wittgenstein’s and is consistent with his view of meaning and rule-following. Semantic (...) supervenience is then defended against two criticisms: first, John McDowell’s suggestion that the supervenience thesis falsifies the epistemology of meaning and fails to accommodate common-sense truths about meaning; second, a series of counter-examples proposed by Stephen Kearns and Ofra Magidor, who argue that worlds may differ semantically without differing non-semantically. It is argued that neither criticism is convincing: we should accept the thesis that semantic facts supervene on non-semantic facts. (shrink)

Stanley Cavell isn't the first to arrive at philosophy through a life with music. Nor is he the first whose philosophical practice bears the marks of that life. Much of Cavell's life with music is confirmed for the world in his philosophical autobiography Little Did I Know. A central moment in that book is Cavell's describing the realization that he was to leave his musical career behind – for what exactly, he did not yet know. He connects the memory-shock of (...) this leaving with "the work of mourning." How does such a life out of music inform Cavell's philosophical sensibility? The thought I follow in this essay is that Cavell's distinctive orientation in philosophy – call this his lifelong coming to terms with his abandoning a life in music – is guided in part by an interest in those moments in experience where words seem to run out, or veer toward nonsense, leaving in their wake touchstones of ecstasy. I explore this idea by summarizing my exchange with Stanley Cavell years ago when I asked him whether certain passages from his essay "Music Discomposed" are depictions of the unsayable. Cavell's response is elaborated, or qualified, by considering a pair of moments in Little Did I Know where words appear to run out. I conclude by discussing culminating thoughts on the burden borne by words and their failure that appear in Cavell's late essay on music, "Impressions of Revolution.". (shrink)

The ancient Stoics believed that virtue is the only true good and as such both necessary and sufficient for happiness. Accordingly, they classified food as among the things that are neither good nor bad but "indifferent." These "indifferents" included health, illness, wealth, poverty, good and bad reputation, life, death, pleasure, and pain. How one deals with having or lacking these things reflects one’s virtue or vice and thus determines one’s happiness or misery. So, while the Stoics held that food in (...) itself contributes nothing to a person’s happiness, how one obtains, prepares, and serves it, and both what and how one eats, all reveal a person’s character as good or bad. Thus, understanding the purpose of food, the necessity of frugality, and the virtue of temperance are all important in Stoicism. This paper traces the ethical views on food from Zeno of Citium and Chrysippus to Seneca, Musonius Rufus, Epictetus, and Marcus Aurelius. They agree that the wise and temperate know that simple, inexpensive foods in moderate amounts produced locally are easy to get and prepare, healthy for the body, and good for the mind. Thus, Stoicism dictates frugality of diet and the rejection of ambitious eating, gluttony, luxuries, delicacies, and gustatory extravagance. Some Stoics favor vegetarianism. All Stoics think it wise to limit eating and drinking to strict bodily need and to eradicate all food anxieties. (shrink)

In this paper, I argue that Kant has a far more communitarian theory of aesthetic life than is usually acknowledged. I focus on two aspects of Kant’s theory that might otherwise be taken to support an individualist reading, namely, Kant’s emphasis on aesthetic autonomy and his characterization of judgments of taste as involving demands for agreement. I argue that the full expression of autonomy in fact requires being a member of an aesthetic community and that within such a community, judgments (...) of taste are issued as invitations to others to engage their faculties towards the goal of shared aesthetic appreciation. (shrink)

In this paper, I argue that although Kant’s account of empirical schemata in the Critique of Pure Reason is primarily used to explain the shared content of intuitions and empirical concepts, it is also informed by methodological problems in natural history. I argue that empirical schemata, which are rules for determining the spatiotemporal form of objects, not only serve to connect individual intuitions with concepts, but also concern the very features of objects on the basis of which they were connected (...) and ordered in taxonomic systems based on similarity of form. I then suggest that Kant likely had scientific illustrations in mind in his discussion of empirical images in the Schematism chapter and that his account of schemata can help explain the epistemic function of these images in early modern science. (shrink)

Bernard Williams famously argued that eternal life is undesirable for a human because it would inevitably grow intolerably boring. I will argue against Williams and those who share his view. To make my case, I will provide an account of what staves off boredom in our current, earthly-mortal lives, and then I will draw on this account while advancing reasons for thinking that eternal life is desirable, given certain conditions. Though my response to Williams will partly overlap with some prior (...) responses to Williams, especially the one offered by J. M. Fischer, my response will also be distinctive in some important ways. For instance, it will be distinctive in that it will discuss the role that one’s part-whole-reality conception plays in fending off boredom, where by “one’s part-whole-reality conception” I mean “one’s conception of his or her place in the whole of reality.”. (shrink)

There is a common misconception across the lntelligence Community (IC) to the effect that information trapped within multiple heterogeneous data silos can be semantically integrated by the sorts of meaning-blind statistical methods employed in much of artificial intelligence (Al) and natural language processlng (NLP). This leads to the misconception that incoming data can be analysed coherently by relying exclusively on the use of statistical algorithms and thus without any shared framework for classifying what the data are about. Unfortunately, such approaches (...) do not yield sustainable results where we are dealing with widely distributed, highly heterogeneous and often changing bodies of data. We argue here that the needed integration requires the use of what we call an lntegrating Semantic Framework (ISF), which provldes a consistent set of categories and relationships that can be reused over and over again to tag successive bodies of data in ways which foster more coherent representation and reasoning. (shrink)

The concept of moral wrongness, many think, has a distinctive kind of referential stability, brought out by moral twin earth cases. This article offers a new account of the source of this stability, deriving it from a metaphysics of content: “substantive” radical interpretation, and first-order normative assumptions. This story is distinguished from extant “reference magnetic” explanations of the phenomenon, and objections and replies are considered.

[This download contains the Table of Contents and Chapter 1]. I argue here that the claim that conscious states are private, in the sense that only one person can ever experience them directly, is false. There actually is a way to connect the brains of two people that would allow one to have direct experience of the other's conscious, e.g., perceptual states. This would allow, for instance, one person to see that the other had deviant color perception (which was masked (...) by correct linguistic practice). This could be achieved by connecting one person's set of executive processes (or cognitive control network) to the conscious perceptual states of the other. Chapter 5 contains an internalist physicalist account of color according to which colors exist only as brain states. Their function is to enable more precise causal interactions between the executive processes and the brain's perceptual systems. This in turn allows for more precise action: I can select the red apples and leave the green ones. (shrink)

A uniform theory of conditionals is one which compositionally captures the behavior of both indicative and subjunctive conditionals without positing ambiguities. This paper raises new problems for the closest thing to a uniform analysis in the literature (Stalnaker, Philosophia, 5, 269–286 (1975)) and develops a new theory which solves them. I also show that this new analysis provides an improved treatment of three phenomena (the import-export equivalence, reverse Sobel-sequences and disjunctive antecedents). While these results concern central issues in the study (...) of conditionals, broader themes in the philosophy of language and formal semantics are also engaged here. This new analysis exploits a dynamic conception of meaning where the meaning of a symbol is its potential to change an agent’s mental state (or the state of a conversation) rather than being the symbol’s content (e.g. the proposition it expresses). The analysis of conditionals is also built on the idea that the contrast between subjunctive and indicative conditionals parallels a contrast between revising and consistently extending some body of information. (shrink)

[This download includes the table of contents and chapter 1.] -/- When we praise, blame, punish, or reward people for their actions, we are holding them responsible for what they have done. Common sense tells us that what makes human beings responsible has to do with their minds and, in particular, the relationship between their minds and their actions. Yet the empirical connection is not necessarily obvious. The “guilty mind” is a core concept of criminal law, but if a defendant (...) on trial for murder were found to have serious brain damage, which brain parts or processes would have to be damaged for him to be considered not responsible, or less responsible, for the crime? The authors argue that evidence from neuroscience and the other cognitive sciences can illuminate the nature of responsibility and agency. They go on to offer a novel and comprehensive neuroscientific theory of human responsibility. (shrink)

The disjunction problem and the distality problem each presents a challenge that any theory of mental content must address. Here we consider their bearing on purely probabilistic causal theories. In addition to considering these problems separately, we consider a third challenge—that a theory must solve both. We call this “the hard problem.” We consider 8 basic ppc theories along with 240 hybrids of them, and show that some can handle the disjunction problem and some can handle the distality problem, but (...) none can handle the hard problem. This is our main result. We then discuss three possible responses to that result, and argue that though the first two fail, the third has some promise. (shrink)

It is natural to say that when we acquire a new concept or concepts, or grasp a new theory, or master a new practice, we come to see things in a new way: we perceive phenomena that we were not previously aware of; we come to see patterns or connections that we did not previously see. That natural idea has been applied in many areas, including the philosophy of science, the philosophy of religion, and the philosophy of language. And, in (...) reflecting on the character of philosophy itself, Wittgenstein himself associates the introduction of a new concept in philosophy with the discovery of a new way of looking at things (PI §401), and says that the point of presenting us with an imagined example may be to change our way of looking at things (PI §144). The paper considers four interrelated questions about this association between seeing-as and change, novelty, or innovation. 1. Is there an important difference between the case where the change in someone’s way of seeing things involves the invention or discovery of a completely new concept, a completely new theory etc., and the case where it involves the person’s coming to understand an existing concept or theory? 2. Is there a special connection between seeing-as and conceptual or theoretical change or creativity: a connection that does not obtain between seeing-as and using or applying a familiar theory or system of concepts? 3. In cases where seeing-as is associated with novelty or creativity, is there any sense in which the fact that someone sees things in a new way can help to explain their conceptual or theoretical creativity? 4. To the extent that there is some association between seeing-as and novelty or creativity, why if at all does it matter that one experiences things in a certain way? Would someone who was aspect-blind be any worse off with respect to creativity or innovation than the rest of us? And if so, why? (shrink)

I explore the thesis that the future is open, in the sense that future contingents are neither true nor false. The paper is divided into three sections. In the first, I survey how the thesis arises on a variety of contemporary views on the metaphysics of time. In the second, I explore the consequences for rational belief of the ‘Aristotelian’ view that indeterminacy is characterized by truth-value gaps. In the third, I outline one line of defence for the Aristotelian against (...) the puzzles this induces: treating opinion about future contingents as a matter of fictional belief rather than simple belief. (shrink)

The hard problem of consciousness has held center stage in the philosophy of mind for the past two decades. It claims that the phenomenal character of conscious experiences—what it’s like to be in them—cannot be explained by appeal to the operation of physiological subsystems. The hard problem arises, however, only given the assumption that hylomorphism is false. Hylomorphism claims that structure is a basic ontological and explanatory principle. A human is not a random collection of physical materials, but an individual (...) composed of physical materials with a structure that accounts for what it is and what it can do—the powers it has. What is true of humans is true of their activities as well. The latter are not random physiological changes, but structured ones: we engage in them by coordinating the ways our parts manifest their powers. Structured activities include perceptual experiences. Consequently, everything about a perceptual experience, including its phenomenal character, can be explained by describing the perceiver’s perceptual subsystems, the powers of those subsystems, and the coordination that unifies their activities into the activity of the perceiver as a whole. Conscious experiences thus fit unproblematically into the natural world—just as unproblematically as the phenomenon of life. Even exponents of the hard problem of consciousness agree that there is no hard problem of life. Consequently, if hylomorphism is true, there can be no hard problem of consciousness. To insist that there is such a problem, then, is implicitly to reject hylomorphism. The concept of consciousness that motivates the hard problem is as much a theoretical construct, therefore, as the concept of life that motivates an obstinate vitalist. (shrink)

I argue that coherence is truth-conducive in that coherence implies an increase in the probability of truth. Central to my argument is a certain principle for transitivity in probabilistic support. I then address a question concerning the truth-conduciveness of coherence as it relates to (something else I argue for) the truth-conduciveness of consistency, and consider how the truth-conduciveness of coherence bears on coherentist theories of justification.

A central theme in Wittgenstein’s post-Tractatus remarks on the limits of language is that we ‘cannot use language to get outside language’. One illustration of that idea is his comment that, once we have described the procedure of teaching and learning a rule, we have ‘said everything that can be said about acting correctly according to the rule’; ‘we can go no further’. That, it is argued, is an expression of anti-reductionism about meaning and rules. A framework is presented for (...) assessing the debate between reductionist and anti-reductionist readings of Wittgenstein’s views about meaning and use. It is argued that that debate cannot be settled merely by reference to Wittgenstein’s general opposition to reductionism. An important argument for anti-reductionism about rules and meaning, from Remarks on the Foundations of Mathematics, is discussed. Putative evidence of reductionism about meaning in the Brown Book is considered; an alternative reading is proposed. The nature of Wittgenstein’s anti-reductionism is examined. It is argued, first, that Wittgenstein accepts that semantic and normative facts supervene on non-semantic, non-normative facts and, second, that at many points his treatment of meaning and rules goes beyond the kind of pleonastic claim that is often taken to define non-reductionist, quietist, positions in philosophy. (shrink)

Coherentists on epistemic justification claim that all justification is inferential, and that beliefs, when justified, get their justification together (not in isolation) as members of a coherent belief system. Some recent work in formal epistemology shows that “individual credibility” is needed for “witness agreement” to increase the probability of truth and generate a high probability of truth. It can seem that, from this result in formal epistemology, it follows that coherentist justification is not truth-conducive, that it is not the case (...) that, under the requisite conditions, coherentist justification increases the probability of truth and generates a high probability of truth. I argue that this does not follow. (shrink)