The question of when human life begins is critical in debates related to life issues. While there are a variety of proposals as to how an organism should be defined, many biologists and ethicists, particularly Catholics, have approached this issue by arguing that fertilization defines the beginning of a new organism. Examining the processes of fission and fusion, which take place before gastrulation, provides strong evidence for when human life beings and therefore how it should be defined. Among the four (...) dominant theories, regulative fission and fusion are the best explanations in terms of being the most consistent with the biological data. This explanation of twinning provides compelling evidence that fertilization is not a necessary condition for human generation, although it may be a sufficient condition. While fertilization generates the vast majority of human beings, additional human beings may rarely be generated during fission events. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Reviewed by:Appearance and Explanation: Phenomenal Explanationism in Epistemology by Kevin McCain and Luca MorettiCaleb EstepMcCAIN, Kevin and Luca Moretti. Appearance and Explanation: Phenomenal Explanationism in Epistemology. Oxford: Oxford University Press, 2021. iv + 195 pp. Cloth, $70.00Since its beginning, phenomenal conservatism (PC) has grown rapidly in popularity as a theory of epistemic justification. In Appearance and Explanation, McCain and Moretti develop out of PC a new theory of justification (...) that they call phenomenal explanationism (PE). Their goal is to integrate PC with explanationism—the view that epistemic justification comes from the best explanation—thereby creating PE as a hybrid theory. They ambitiously contend that PE captures the same basic intuitions as PC but is better equipped to handle epistemic phenomena as a whole, troubling objections to PC (and foundationalism in general), and skeptical [End Page 354] arguments. The book is comprised of seven chapters. This review will emphasize the first four.In chapter 1, the authors discuss what PC is and its merits. PC is the idea that "we should grant things to be the way they appear [or seem] to be, unless we have reason to doubt" our seemings. They point out some of the benefits of PC as perceived by its followers: It "provide[s] widespread epistemic practices with a rationale," "it offers a unified account of non-inferential justification for beliefs of very different types," "it constitutes the basis of fallible foundationalism," and has a strong "antiskeptical bite."In chapter 2, McCain and Moretti argue that PC is not sufficient to account even for noninferential justification. First, they argue, PC gives an insufficient explanation of the no-defeater condition. The no-defeater condition is the "unless we have reason to doubt" clause built into PC. PC does not explain why or how S's reason to doubt "interacts with S's seeming that e in such a way as to diminish S's non-inferential justification for believing p." Second, if the power of seemings to justify comes from the seemings themselves, then the seemings become unstable once the subject becomes aware of them. The upshot of this is that if seemings are sufficient for justification, then some beliefs that should not be justified would have justification.In chapter 3, the authors begin to elaborate on their view. The authors distinguish between mere seemings, paired appearances, and presentational appearances to show how appearances can have varying degrees of justificatory power. Seemings and appearances are used in a roughly synonymous way. Mere seemings are lacking in both sensations and presentational phenomenology, hence they provide a very weak form of justification. Paired appearances have sensations but not presentational phenomenology. They have greater justificatory strength than mere seemings but less strength than presentational appearances. Presentational appearances produce the strongest justification and include both sensations and presentational phenomenology. The big payoff from these distinctions is that they show how different appearances can produce varying strengths of justification.In chapter 4, Moretti and McCain first outline their version of explanationism, which is evidentialist in character. It is as follows: "Believing p is justified for S at t if and only if at t:(1). S has total evidence, E;(2). either (i) p is the best (sufficiently good) explanation of e (where e is a subset of E), or (ii) p is an explanatory consequence of the best (sufficiently good) explanation of e (where p is such an explanatory consequence if and only if the relevant explanation of e would provide an explanation of p's truth that is significantly better than the explanation it would provide of ~ p's truth);(3). it is not the case that p fails to satisfy (i) and (ii) with respect to e because of the additional evidence included in E." [End Page 355]Next, the authors merge explanationism with PC as understood through the threefold division of appearances given in chapter 3. The result is that appearances or seemings are necessary and sufficient for a subject to have evidence, but the subject is justified in believing some proposition p only because p is the best explanation of the evidence. Appearances contribute to epistemic justification because as evidence they regulate the capacity... (shrink)