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)

Amartya Sen has made a major contribution to the theory of social justice, and of gender justice, by arguing that capabilities are the relevant space of comparison when justice-related issues are considered. This article supports Sen's idea, arguing that capabilities supply guidance superior to that of utility and resources (the view's familiar opponents), but also to that of the social contract tradition, and at least some accounts of human rights. But I argue that capabilities can help us to construct a (...) normative conception of social justice, with critical potential for gender issues, only if we specify a definite set of capabilities as the most important ones to protect. Sen's "perspective of freedom" is too vague. Some freedoms limit others; some freedoms are important, some trivial, some good, and some positively bad. Before the approach can offer a valuable normative gender perspective, we must make commitments about substance. (shrink)

Much of the discussion surrounding the ethics of abortion has centered around the notion of personhood. This is because many philosophers hold that the morality of abortion is contingent on whether the fetus is a person - though, of course, some famous philosophers have rejected this thesis (e.g. Judith Thomson and Don Marquis). In this article, I construct a novel argument for the immorality of abortion based on the notion of impairment. This argument does not assume that the fetus is (...) a person - indeed, I concede (for the sake of argument) that the fetus is not a person - and hence the morality of abortion is not contingent on whether the fetus is a person. I finish by answering a plethora of objections to my argument, concluding that none of them are successful. (shrink)

One of HLA Hart's main contributions to jurisprudence is his theory of social rules. Hart said, essentially, that a social rule exists if the members of a society act in some way and have a certain attitude. Most legal philosophers think that Hart's account of this attitude is too general, however, and that his theory is overinclusive as a result. In this article, I draw on recent work in the philosophy of action to propose a more precise account of the (...) relevant attitude, and a revised version of Hart's theory. I claim that a social rule exists if the members of a society act in some way and ‘accept’ they ought to act this way, independent of their beliefs about the matter. One of the implications of this idea is that the attitude that underlies a social rule is closely analogous to a presumption or fiction about what ought to be done. -/- . (shrink)

It is often assumed that if the fetus is a person, then abortion should be illegal. Thomson1 laid the groundwork to challenge this assumption, and Boonin2 has recently argued that it is false: he argues that abortion should be legal even if the fetus is a person. In this article, I explain both Thomson’s and Boonin’s reason for thinking that abortion should be legal even if the fetus is a person. After this, I show that Thomson’s and Boonin’s argument for (...) legalised abortion fail; they have not given us good reason for thinking abortion should be legal.1 Finally, I argue that—if we play Boonin’s game—abortion should be illegal. When discussing the ethics and politics of abortion, whether the fetus is a person is usually central.3 4.2 However, Thomson1 long ago challenged this view. She argued that abortion is permissible even if the fetus is a person. To do so, she asks us to consider a case in which you are non-consensually taken to a hospital and hooked up to a famous violinist. The violinist, if he is to survive, needs to filter his blood through your body. After 9 months, he will be fine and you can unplug yourself and go on your way. If you unplug yourself prior to this, however, he will die. Is it permissible to unplug yourself? Thomson thinks the answer is ‘yes’. And this, she thinks, shows that abortion is permissible even if the fetus is a person. While the majority of her article focuses on the ethics of abortion, it is clear that she also aims to show that abortion should be legal if the fetus is a person; she would no doubt reject the view that the state is right to coerce you into …. (shrink)

In cases in which we must choose between either (i) preventing a woman from remaining unwillingly pregnant or (ii) preventing a fetus from being killed, we should prevent the fetus from being killed. But this suggests that in typical cases abortion is wrong: typical abortions involve preventing a woman from remaining unwillingly pregnant over preventing a fetus from being killed. And so abortion is typically wrong—and this holds whether or not fetuses are persons.

Demonstratives seem to have posed a severe difficulty for Frege’s philosophy of language, to which his doctrine of incommunicable senses was a reaction. In “The Thought,” Frege briefly discusses sentences containing such demonstratives as “today,” “here,” and “yesterday,” and then turns to certain questions that he says are raised by the occurrence of “I” in sentences (T, 24-26). He is led to say that, when one thinks about oneself, one grasps thoughts that others cannot grasp, that cannot be communicated. However, (...) nothing could be more out of the spirit of Frege’s account of sense and thought than an incommunicable, private thought. In the first part of the paper, I explain the problem demonstratives pose for Frege, and explore three ways he might have dealt with it. I argue that none of these ways provides Frege with a solution to his problem consistent with his philosophy of language. The first two are plausible as solutions, but contradict his identification of the sense expressed by a sentence with a thought. The third preserves the identification, but is implausible. In the second part, I suggest that Frege was led to his doctrine of incommunicable senses as a result of some appreciation of the difficulties his account of demonstratives faces, for these come quickly to the surface when we think about “I.” I argue that incommunicable senses won’t help. I end by trying to identify the central problem with Frege’s approach, and sketching an alternative. (shrink)

This article motivates and develops a reductive account of the structure of certain physical quantities in terms of their mereology. That is, I argue that quantitative relations like "longer than" or "3.6-times the volume of" can be analyzed in terms of necessary constraints those quantities put on the mereological structure of their instances. The resulting account, I argue, is able to capture the intuition that these quantitative relations are intrinsic to the physical systems they’re called upon to describe and explain.

Legal discourse consists largely of legal claims. These are claims that there is a legal obligation, legal right, or other legal incident. What is the meaning of “legal obligation”, “legal right” and so on in legal claims? The standard view among philosophers of law is that “legal” indicates that, according to law, there is a moral obligation, moral right or other moral incident. Here I set out a new objection to the standard view. The objection is that the standard view (...) is unable to account for the use of legal claims in some common forms of logically complex arguments. (shrink)

In my article "Even if the fetus is not a person, abortion is immoral: The impairment argument" (this journal), I defended what I called “The impairment argument” which purports to show that abortion is immoral. Bruce Blackshaw (2019) has argued that my argument fails on three accounts. In this article, I respond to his criticisms.

Throughout the COVID-19 pandemic, shortages of scarce healthcare resources consistently presented significant moral and practical challenges. While the importance of vaccines as a key pharmaceutical intervention to stem pandemic scarcity was widely publicized, a sizable proportion of the population chose not to vaccinate. In response, some have defended the use of vaccination status as a criterion for the allocation of scarce medical resources. In this paper, we critically interpret this burgeoning literature, and describe a framework for thinking about vaccine-sensitive resource (...) allocation using the values of responsibility, reciprocity, and justice. Although our aim here is not to defend a single view of vaccine-sensitive resource allocation, we believe that attending critically with the diversity of arguments in favor (and against) vaccine-sensitivity reveals a number of questions that a vaccine-sensitive approach to allocation should answer in future pandemics. (shrink)

This article is a response to Stephen Law's article ‘The evil-god challenge’. In his article, Law argues that if belief in evil-god is unreasonable, then belief in good-god is unreasonable; that the antecedent is true; and hence so is the consequent. In this article, I show that Law's affirmation of the antecedent is predicated on the problem of good (i.e. the problem of whether an all-evil, all-powerful, and all-knowing God would allow there to be as much good in the world (...) as there is), and argue that the problem of good fails. Thus, the antecedent is unmotivated, which renders the consequent unmotivated. Law's challenge for good-god theists is to show that good-god theism is not rendered unreasonable by the problem of evil in the same way that evil-god theism is rendered unreasonable by the problem of good. Insofar as the problem of good does not render belief in evil-god unreasonable, Law's challenge has been answered: since it is not unreasonable to believe in evil-god (at least for the reasons that Law gives) it is not unreasonable to believe in good-god. Finally, I show that – my criticism aside – the evil-god challenge turns out to be more complicated and controversial than it initially appears, for it relies on the (previously unacknowledged) contentious assumption that sceptical theism is false. (shrink)

I provide an updated version of The Impairment Argument against abortion and respond to numerous objections that can be (and have been) raised to it.

Skeptical theism is a popular response to arguments from evil. Many hold that it undermines a key inference often used by such arguments. However, the case for skeptical theism is often kept at an intuitive level: no one has offered an explicit argument for the truth of skeptical theism. In this article, I aim to remedy this situation: I construct an explicit, rigorous argument for the truth of skeptical theism.

A pardon is an act of mercy according to the law, but is a pardon mercy in an ordinary or genuine sense? What distinguishes a pardon from a lenient judicial sentence, which is not mercy by the law’s lights? These are questions about what mercy as it is understood in law has to do with mercy as it is understood outside of law, and about who in government acts mercifully and when, if indeed anyone in government ever does. Here I (...) propose a general analysis of mercy, then bring that analysis to bear on government action. Three features of my analysis are noteworthy. First, almost all existing analyses say that mercy is unconstrained in a normative sense, but I argue that mercy is unconstrained in the way that arbitrary power is unconstrained. Second, although it’s often assumed that mercy must be motivated by compassion, I show that mercy only requires acting with the intention to benefit the recipient. Third, my analysis says that mercy requires the giver of mercy to overcome a motivation to treat the recipient harshly. Given this analysis, few government acts are merciful, but pardon is an institutional approximation or analog of mercy. -/- . (shrink)

Critics of skeptical theism often claim that if it (skeptical theism) is true, then we are in the dark about whether (or for all we know) there is a morally justifying for God to radically deceive us. From here, it is argued that radical skepticism follows: if we are truly in the dark about whether there is a morally justifying reason for God to radically deceive us, then we cannot know anything. In this article, I show that skeptical theism does (...) not entail that we are in the dark about whether (or for all we know) there is a morally justifying reason for God to deceive us. And hence arguments against skeptical theism that make use of this assumption fail. (shrink)

Arguments from evil purport to show that some fact about evil makes it (at least) probable that God does not exist. Skeptical theism is held to undermine many versions of the argument from evil: it is thought to undermine a crucial inference that such arguments often rely on. Skeptical objections to skeptical theism claim that it (skeptical theism) entails an excessive amount of skepticism, and therefore should be rejected. In this article, I show that skeptical objections to skeptical theism have (...) a very limited scope: only those who reject certain (apparently) popular epistemological theories will be threatened by them. (shrink)

Abortion restrictions are particularly good for black women—at least in the United States. This claim will likely strike many as outlandish. And numerous commentaries on abortion restrictions have suggested otherwise: many authors have lamented the effects of abortion restrictions on women, and black women in particular—these restrictions are bad for them, these authors say. However, abortion restrictions are clearly good for black women. This is because if someone is prevented from performing a morally wrong action, it’s good for her. For (...) example, it’s good for Sarah if she’s prevented from driving home drunk. However, since abortion is morally wrong, it follows that it’s good for women when they are prevented from getting an abortion. And since black women get abortions at disproportionately high rates, abortion restrictions are good in particular for black women. Indeed, this is an example of a positive effect of intersectionality. (shrink)

The “Embryo Rescue Case” (ERC) refers to a thought experiment that is used to argue against the view that embryos have a right to life (i.e. are persons). I will argue that cognitive science undermines the intuition elicited by the ERC; I will show that whether or not embryos have a right to life, our mental tools will make it very difficult to believe that embryos have said right. This suggests that the intuition elicited by the ERC is not truth (...) indicative. The upshot of this is that we have an undercutting defeater for our intuition that embryos do not have a right to life. (shrink)

Healthcare practitioners have access to a range of ethical guidance. However, the normative role of this guidance in ethical decision-making is underexplored. This paper considers two ways that healthcare practitioners could approach ethics guidance. We first outline the idea of deference to ethics guidance, showing how an attitude of deference raises three key problems: moral value; moral understanding; and moral error. Drawing on philosophical literature, we then advocate an alternative framing of ethics guidance as a form of moral testimony by (...) colleagues and suggest that a more promising attitude to ethics guidance is to approach it in the spirit of ‘critical engagement’ rather than deference. (shrink)

Tradução do artigo "Mill between Aristotle and Bentham".

Joona Räsänen, in his article ‘Ectogenesis, abortion and a right to the death of the fetus’, has argued for the view that parents have a right to the death of the fetus. In this article, I will explicate the three arguments Räsänen defends, and show that two of them have false or unmotivated premises and hence fail, and that the support he offers for his third argument is inconsistent with other views he expresses in his article. Therefore, I conclude that (...) there is no right to the death of the fetus—or, if there is one, Räsänen has not shown it. (shrink)

Trent Dougherty has argued that commonsense epistemology and skeptical theism are incompatible. In this paper, I explicate Dougherty’s argument, and show that (at least) one popular form of skeptical theism is compatible with commonsense epistemology.

I’ve argued that those who endorse the argument from divine hiddenness must give up all pure de jure objections to theism, and this means that endorsing the argument is costly for atheists. Benjamin Curtis claims that this isn’t a significant cost for atheists. I show that—contrary to Curtis—there is a significant cost, and spell out why this is so. Furthermore, I show that my argument functions as a new argument for affirming reformed epistemology—the view that if theism is true, belief (...) in God is probably rational. (shrink)

De facto objections to theism purport to show that theism is false, whereas de jure objections to theism claim that, whether or not theism is true, belief in God is irrational. Divine hiddenness – the fact that there are people who non-resistantly lack belief in God – is sometimes used as an argument against theism. In this article I will show that accepting the argument from divine hiddenness carries a high cost: it eliminates all de jure objections to theism. So (...) atheists can either have de jure objections to theism or the objection from divine hiddenness, but they cannot have both. (shrink)

P-zombies are creatures that are physically (functionally, behaviorally) like you and I and yet lack phenomenal consciousness. If such creatures are possible, it’s (typically) taken to show property dualism is true: phenomenal consciousness isn’t reducible to—nor does it supervene on—physical states. If inverted qualia are possible, it’s possible that you and I have identical physical states and yet you see tomatoes as green and I see tomatoes as red. If this is the case, then (again) property dualism is (typically) taken (...) to be true. In this article, I’ll show that p-zombies and inverted qualia—if they are actually possible—prove more than previously thought: if one thinks p-zombies or inverted qualia are possible, then she should endorse one of the four following theses: (i) substance dualism, (ii) we have even more reason to reject p-zombies and inverted qualia since they entail an even more radical conclusion than previously thought (i.e. substance dualism), (iii) eliminativism about selves, or (iv) friends of p-zombies and inverted qualia have homework: they need to show a relevant, plausible disanalogy between arguments for p-zombies and inverted qualia as traditionally stated and my parallel arguments that entail substance dualism. My purpose here isn’t to defend any of these particular options. Instead, my purpose is to highlight that these are the four options available to take. (shrink)

Dignity is traditionally thought to apply to almost all and almost only humans. However, I argue that an account of a distinctly human dignity cannot achieve a coherent and non-arbitrary justification; either it must exclude some humans or include some nonhumans. This conclusion is not as worrying as might be first thought. Rather than attempting to vindicate human dignity, dignity should extend beyond the human, to include a range of nonhuman animals. Not only can we develop a widely inclusive account (...) of dignity by pursuing this route, but we can still defend the three core principles that lie at the heart of contemporary thinking about dignity: that bearers of dignity possess dignity to an equal degree, in virtue of possessing the same intrinsic worth, and that this generates direct and claimable rights. I thus develop an account of dignity that includes nonhuman animals. I argue that the capacity to value most plausibly grounds dignity. This capacity arises from valenced sentience: a being values insofar as they have experiences that matter to them. I then characterise what follows from this. First, I contend that it is only the capacity to value grounds dignity because this produces the most plausible, simplest, and most explanatorily powerful account of dignity. We ought to reject pluralist accounts which assert a sharp distinction between bearers and non-bearers of rational agency, and biocentric accounts which include non-sentient organic entities. Second, I argue this property grounds an account of dignity that is non-hierarchical. There are no degrees of dignity. Instead, all possessors of the capacity to value have the same kind of intrinsic value, and the same equal fundamental right: to consideration of their interest in leading a life of value. Finally, I argue that since the fundamental right is to consideration, moral agents have claimable duties to engage in a deliberative procedure with actionable requirements. Specific rights are instantiations of this general procedure. Certain revisionist conclusions follow on my view, for instance, that nonhumans should be given greater weight and inclusion in a far wider range of cases, but my account is sensitive to the range of different things different beings value, so it does not generate counterintuitive implications. I conclude that dignity extends beyond the human. (shrink)

Tim Maudlin has influentially argued that Humeanism about laws of nature stands in conflict with quantum mechanics. Specifically Humeanism implies the principle Separability: the complete physical state of a world is determined by the intrinsic physical state of each space-time point. Maudlin argues Separability is violated by the entangled states posited by QM. We argue that Maudlin only establishes that a stronger principle, which we call Strong Separability, is in tension with QM. Separability is not in tension with QM. Moreover, (...) while the Humean requires Separability to capture the core tenets of her view, there's no Humean-specific motivation for accepting Strong Separability. We go on to give a Humean account of entangled states which satisfies Separability. The core idea is that certain quantum states depend upon the Humean mosaic in much the same way as the laws do. In fact, we offer a variant of the Best System account on which the systemization procedure that generates the laws also serves to ground these states. We show how this account works by applying it to the example of Bohmian Mechanics. The 3N-dimensional configuration space, the world particle in it and the wave function on it are part of the best system of the Humean mosaic, which consists of N particles moving in 3-dimensional space. We argue that this account is superior to the Humean account of Bohmian Mechanics defended by Loewer and Albert, which takes the 3N-dimensional space, and its inhabitants, as fundamental. (shrink)

Although better known for his phenomenology of perception and the perceived world, Merleau-Ponty’s writings also contain the outlines of a rich and unique account of the imagination and the imaginary. In this paper, I explicate the phenomenology of the image that Merleau-Ponty develops throughout his work. I show how Merleau-Ponty develops this account of the image in critical response to Sartre and in a way that follows from his own descriptions of what painters do when they paint and of what (...) we experience when we look at their paintings. The investigation of the particular mode of being of images leads to a consideration of the body and Merleau-Ponty’s later ontology. (shrink)

In this paper, I defend the agent/patient distinction against critics who argue that causal interactions are symmetrical. Specifically, I argue that there is a widespread type of causal interaction between distinct entities, resulting in a type of ontological asymmetry that provides principled grounds for distinguishing agents from patients. The type of interaction where the asymmetry is found is when one of the entities undergoes a change in kind, structure, powers, or intrinsic properties as a result of the interaction while the (...) other does not. Interactions of this type are widespread in molecular biology and chemistry. I focus specifically on (i) the actions of enzymes on substrates and (ii) water molecules breaking the bonds of polarized molecules. Finally, I respond to objections by laying out and to a limited extent defending three commitments of my account: emergent entities and powers, realism about chemical kinds or structures, and the assumption of the agent/patient distinction in functional attributions in biology. (shrink)

The pelvic exam is used to assess the health of female reproductive organs and so involves digital penetration by a physician. However, it is common practice for medical students to acquire experience in administering pelvic exams by performing them on unconscious patients without prior authorization. In this article, we argue that such unauthorized pelvic exams (UPEs) are sexual assault. Our argument is simple: in any other circumstance, unauthorized digital penetration amounts to sexual assault. Since there are no morally significant differences (...) between UPEs and other instances of digital penetration, UPEs are sexual assault. So, insofar as one is against sexual assault, one should be against UPEs. (shrink)

Lougheed argues that a possible solution to the problem of divine hiddenness is that God hides in order to increase the axiological value of the world. In a world where God exists, the goods associated with theism necessarily obtain. But Lougheed also claims that in such a world it’s possible to experience the goods of atheism, even if they don’t actually obtain. This is what makes a world with a hidden God more valuable than a world where God is unhidden, (...) and also more valuable than an atheistic world with no God. We show that Lougheed never considers the comparison between a world where God hides and an atheistic world. We argue that it’s possible for a person to experience theistic goods in a world where God does not exist, a possibility Lougheed never considers. If this is right it undermines his axiological solution to divine hiddenness. We conclude by showing how our discussion of the axiology of theism connects to the existential question of whether God exists; that is, we show that the axiological question is dependent on the existential question. (shrink)

The topic of this essay is “the slingshot,” a short argument that purports to show that sentences1 designate (stand for, refer to) truth values. Versions of this argument have been used by Frege 2, Church 3, Quine4 and Davidson5; thus it is historically important, even if it immediately strikes one as fishy. The argument turns on two principles, which I call substitution and redistribution. In “Semantic Innocence and Uncompromising Situations,”6 Jon Barwise and I rejected both principles, as part of our (...) attempt.. (shrink)

The study investigated the management of students’ academic failure among secondary school students for high productivity in Obingwa Local Government Area of Abia State. The study was guided by two research questions and two hypotheses. Descriptive survey research design was used while the population of the study comprised thirty public secondary schools. A sample size of 10 secondary schools was selected from the 30 public secondary schools using stratified random sampling technique. Self-designed instrument entitled “Management Students’ Academic Failure Questionnaire” (MSAFQ) (...) was utilized. The validity of the instrument was ensured. Test retest method was used and reliability co-efficient of 0.80 and 0.83 was obtained through Cronbach Alpha Statistics. Mean was used to answer the research questions while Z-test statistics was used to test the hypotheses at 0.05 level of significant. The findings include but not limited to: lack of instructional material and inability of the teachers to stimulate students are causes of academic failures among students. It is therefore recommended that the government or appropriate agency should ensure adequate supply of functional instructional resources and teachers’ should do well to motivate students to learn thereby save students from incessant failures that could mar their future and life expectations. (shrink)

Skeptical theism is a popular response to arguments from evil. Recently, Matthew A. Benton, John Hawthorne, and Yoaav Isaacs have argued that the theses that ground skeptical theism are either false or limited in scope. In this article, I show that their objections rest on dubious assumptions about the nature of skeptical theism. Along the way, I develop and clarify the ambiguous parts of skeptical theism. The upshot of this is that—once the nature of skeptical theism is made clearer—it is (...) far more difficult to resist. (shrink)

In this paper, I consider Sterba’s recent criticism of skeptical theism in context of his argument from evil. I show that Sterba’s criticism of skeptical theism shares an undesirable trait with all past criticisms of skeptical theism: it fails. This is largely due to his focus on causal connections and his neglect of logical connections. Because of this, his argument remains vulnerable to skeptical theism.

Self, person, and identity are among the concepts most central to the way humans think about themselves and others. It is often natural in biology to use such concepts; it seems sensible to say, for example, that the job of the immune system is to attack the non-self, but sometimes it attacks the self. But does it make sense to borrow these concepts? Don’t they only pertain to persons, beings with sophisticated minds, and perhaps even souls? I argue that if (...) we focus on the every-day concepts of self and identity, and set aside loftier concepts found in religion, philosophy, and psychology that are applicable, at most, to humans, we can see that self and identity can be sensibly applied widely in biology. (shrink)

Stephen Davies taught philosophy at the University of Auckland, Auckland, New Zealand. His research specialty is the philosophy of art. He is a former President of the American Society for Aesthetics. His books include Definitions of Art (Cornell UP, 1991), Musical Meaning and Expression (Cornell UP, 1994), Musical Works and Performances (Clarendon, 2001), Themes in the Philosophy of Music (OUP, 2003), Philosophical Perspectives on Art (OUP, 2007), Musical Understandings and Other Essays on the Philosophy of Music (OUP, 2011), The Artful (...) Species: Aesthetics, Art, and Evolution (OUP, 2012), The Philosophy of Art (Wiley-Blackwell, 2016 second ed.), and Adornment: What Self-decorations Tells Us about Who We Are, (Bloomsbury Academic, 2020). (shrink)

Bergson identifies multiple forms of memory throughout his work. In Matter and Memory, Bergson considers memory from the perspectives of both psychology and metaphysics, and he describes what we might refer to as contraction memory, perception memory, habit memory, recollection memory, and pure memory. Further, in subsequent works, Bergson discusses at least two additional forms of memory – namely, a memory of the present and a non-intellectual memory of the will. However, it is often not clear how these different forms (...) of memory relate to one another. With the aim of providing an overview of Bergson's philosophy of memory that can also serve as a point of entry to his philosophy as a whole, this article explores the different senses and forms of memory that Bergson describes, paying special attention to how they are distinct from one another and how they are unified. It is my intention to show that, although these various senses and forms of memory are different from one another , they are also continuous and unified insofar as they are equivalent to different tones of one's mental life and to different tensions of one duration. (shrink)

The word “intolerance” bears almost exclusively negative connotations. It is treated invariably, almost ideologically as a vice. What would it mean to reconceive of intolerance as a virtue—or, at the very least, a positive affect? In this essay, I analyze two complementary archives of positive intolerance: the records of the Prisons Information Group (the GIP) and the writings of one of its members: Michel Foucault. For the GIP, intolerance—as a militant refusal of intolerable material and political conditions—is essential to the (...) prison activist effort. Relatedly, for Foucault, scholarship—as the creative and/or critical act of naming and changing public awareness of intolerable conditions—can be a mode of political intolerance against an oppressive state. When paired together, these two archives trouble the easy severance of theory and practice, suggesting both that prison resistance efforts involve intellectual assessments of the intolerable and that engaged scholarship often doubles as intolerant activism. Both archives, moreover, agree that such intolerant activism is always rooted in personal investments and local struggles. This analysis allows me to suggest that, if the struggle against forces of marginalization and exploitation mobilizes resistant intolerance as a political and intellectual strategy, then intolerance may very well be commendable. It might, in fact, be virtuous. (shrink)

Perry Hendricks’ impairment argument for the immorality of abortion is based on two premises: first, impairing a fetus with fetal alcohol syndrome is immoral, and second, if impairing an organism to some degree is immoral, then ceteris paribus, impairing it to a higher degree is also immoral. He calls this the impairment principle. Since abortion impairs a fetus to a higher degree than FAS, it follows from these two premises that abortion is immoral. Critics have focussed on the ceteris (...) paribus clause of TIP, which requires that the relevant details surrounding each impairment be sufficiently similar. In this article, we show that the ceteris paribus clause is superfluous, and by replacing it with a more restrictive condition, the impairment argument is considerably strengthened. There are no data in this work. (shrink)

Perry Hendricks’ original impairment argument for the immorality of abortion is based on the impairment principle (TIP): if impairing an organism to some degree is immoral, then ceteris paribus, impairing it to a higher degree is also immoral. Since abortion impairs a fetus to a higher degree than fetal alcohol syndrome (FAS) and giving a fetus FAS is immoral, it follows that abortion is immoral. Critics have argued that the ceteris paribus is not met for FAS and abortion, and (...) so we proposed the Modified Impairment Principle (MIP) to avoid these difficulties. Dustin Crummett has responded, arguing that MIP is open to various counterexamples which show it to be false. He also shows that MIP can generate moral dilemmas. Here, we propose a modification to MIP that resolves the issues Crummett raises. Additionally, Alex Gillham has criticized our appropriation of Don Marquis’ ‘future like ours’ reasoning about the wrongness of impairment. We show that his objections have minimal implications for our argument. (shrink)

This paper is a response to Tyler Wunder’s ‘The modality of theism and probabilistic natural theology: a tension in Alvin Plantinga's philosophy’ (this journal). In his article, Wunder argues that if the proponent of the Evolutionary Argument Against Naturalism (EAAN) holds theism to be non-contingent and frames the argument in terms of objective probability, that the EAAN is either unsound or theism is necessarily false. I argue that a modest revision of the EAAN renders Wunder’s objection irrelevant, and that this (...) revision actually widens the scope of the argument. (shrink)

The ethics of abortion considers whether abortion is immoral. Pro-choice philosophers think that it is not immoral, while pro-life philosophers think that it is. The axiology of abortion considers whether world would be better if the pro-choice or pro-life position is right. While much attention has been given to the ethics of abortion, there has been no attention given to the axiology of abortion. In this article, I seek to change that. I consider various arguments for thinking our world would (...) be better if the pro-choice position or the pro-life position is correct, ultimately concluding that it would be better if the pro-choice position is right. This is unfortunate, however, since there is no good reason to think the pro-choice position is correct. (shrink)

The subject’s perspective objection (SPO) is an objection against externalist theories of justification, warrant, and knowledge. In this article, I show that externalists can accommodate the SPO while remaining externalist. So, even if the SPO is successful, it does not motivate internalism, and the primary motivation for internalism has been lost. After this, I provide an explanation for why so many people find cases that motivate the SPO convincing.

We argue that the evil-god challenge is not an additional challenge for theists above and beyond the (much older) gap problem. One version of the evil-god challenge is merely a specific instance of the gap problem, and another is dependent on that specific instance of the gap problem. Therefore, the various solutions to the gap problem that theists have developed double as responses to the evil-god challenge, placing the evil-god challenge in a more vulnerable position than has been supposed.

Spanish version of collaborative essay with Oaxaca-based Mexican experimental filmmaker Bruno Varela on his found footage project La máquina de futuro. Published on the website Los Experimentos together with the release of Varela's diptych Anáhuac contra los robots, consisting of the films La máquina de futuro and La ranura en el tiempo.