Whenever some form of beneficent killing--for example, voluntary euthanasia--is advocated, the proposal is greeted with a flood of slippery-slope arguments warning of the dangers of a Nazi-style slide into genocide. This paper is an attempt systematically to evaluate arguments of this kind. Although there are slippery-slope arguments that are sound and convincing, typical formulations of the Nazi-invoking argument are found to be seriously deficient both in logical rigour and in the social history and psychology required as a scholarly underpinning. As an antidote, an attempt is made both to identify some of the likely causes of genocide and to isolate some of the more modest but legitimate fears that lie behind slippery-slope arguments of this kind.

In this paper we attempt to sharpen and to provide an answer to the question of when human beings first become conscious. Since it is relatively uncontentious that a capacity for raw sensation precedes and underpins all more sophisticated mental capacities, our question is tantamount to asking when human beings first have experiences with sensational content. Two interconnected features of our argument are crucial. First, we argue that experiences with sensational content are supervenient on facts about electrical activity in the cerebral cortex which can be ascertained through EEG readings. Second, we isolate from other notions of a 'functioning brain' that which is required to underpin the view that a cortex is functioning in a way which could give rise to rudimentary conscious experiences. We investigate the development in the human fetus of the anatomical and chemical pathways which underpin (immature) cortical activity and the growth and maturation of the electrical circuitry specifically associated with sensational content in adult experience. We conclude (tentatively) that a fetus becomes conscious at about 30 to 35 weeks after conception; an answer based on a careful analysis of EEG readings at various stages of cortical development. Finally, we survey the possible ethical ramifications of our answer.

This paper re-examines the question of whether quirks of early human foetal development tell against the view (conceptionism) that we are human beings at conception. A zygote is capable of splitting to give rise to identical twins. Since the zygote cannot be identical with either human being it will become, it cannot already be a human being. Parallel concerns can be raised about chimeras in which two embryos fuse. I argue first that there are just two ways of dealing with cases of fission and fusion and both seem to be available to the conceptionist. One is the Replacement View according to which objects cease to exist when they fission or fuse. The other is the Multiple Occupancy View - both twins may be present already in the zygote and both persist in a chimera. So, is the conceptionist position tenable after all? I argue that it is not. A zygote gives rise not only to a human being but also to a placenta - it cannot already be both a human being and a placenta. Neither approach to fission and fusion can help the conceptionist with this problem. But worse is in store. Both fission and fusion can occur before and after the development of the inner cell mass of the blastocyst - the entity which becomes the embryo proper. The idea that we become human beings with the arrival of the inner cell mass leads to bizarre results however we choose to accommodate fission and fusion.

I aim to show how and why some definitions can be benignly circular. According to Lloyd Humberstone, a definition that is analytically circular need not be inferentially circular and so might serve to illuminate the application‐conditions for a concept. I begin by tidying up some problems with Humberstone's account. I then show that circular definitions of a kind commonly thought to be benign have inferentially circular truth‐conditions and so are malign by Humberstone's test. But his test is too demanding. The inferences we actually use to establish the applicability of, e.g., colour concepts are designed to establish warranted assertability and not truth. Understood thus, dispositional analyses are not inferentially circular.

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