In this paper I will examine two responses to the argument from marginal cases; the argument from kinds and the similarity argument. I will argue that these arguments are insufficient to show that all humans have moral status but no animals do. This does not prove that animals have moral status but it does shift the burden of proof onto those who want to maintain that all humans are morally considerable, but no animals are.

This article explores Peter Singer’s Animal Liberation thesis and examines the arguments against his work, particularly from certain moral philosophers in the late 1970s and 1980s who seriously engaged with his ideas. This article argues that due to the straightforward, minimalist nature of Singer’s preference utilitarianism, his arguments have remained highly defensible and persuasive. By advancing sentience, above characteristics like intelligence or rationality, as a sufficient criterion for possessing interests, Singer provides a justifiable principle for morally considering animal interests equal (...) to those of humans. Numerous moral philosophers have challenged Singer, but they have struggled to seriously counter his core principle and to resolve the argument of ‘marginal cases’—that is, why do infants and intellectually disabled humans have moral status and animals do not. Ultimately, Singer broadly challenged prevailing anthropocentric views of animals and, in some instances, persuaded some of his most intransigent opponents. (shrink)

In this article, I consider a number of arguments that assume that beings who have immortal souls occupy a special position in the sphere of moral concern. First, I place these arguments in their historical and cultural contexts. Next, I formulate several conditions of adequacy that all such arguments must satisfy. Subsequently, I distinguish two different general kinds of such arguments: Inclusionary arguments attempt to use the immortality of soul as a criterion for either including someone into a sphere of (...) morality while excluding others or, at least, for elevating someone's position within this sphere. Modifying arguments attempt to strengthen or weaken moral considerations that already apply to a being included into the sphere of morality. I argue that, although some modifying arguments may fulfill all conditions of adequacy, they have very little practical importance. (shrink)

If we are going to treat other species so very differently from our own — killing, eating and experimenting on pigs and sheep, for example, but never human beings — then it seems we need to come up with some morally relevant difference between us and them that justifies this difference in treatment. Otherwise it appears we are guilty of bigotry (in just the same way that someone who discriminates on the basis of race or sex is guilty of bigotry). (...) But what is this morally relevant difference? Julia Tanner's article examines, and rejects, some of the most popular answers to this question. -/- . (shrink)

Rationality (or something similar) is usually given as the relevant difference between all humans and animals; the reason humans do but animals do not deserve moral consideration. But according to the Argument from Marginal Cases not all humans are rational, yet if such (marginal) humans are morally considerable despite lacking rationality it would be arbitrary to deny animals with similar capacities a similar level of moral consideration. The slippery slope objection has it that although marginal humans are not strictly speaking (...) morally considerable, we should give them moral consideration because if we do not we will slide down a slippery slope where we end up by not giving normal humans due consideration. I argue that this objection fails to show that marginal humans have the kind of direct moral status proponents of the slippery slope argument have in mind. (shrink)