I here discuss an argument frequently dismissed as a fallacy – the slippery slope or camel's nose. The argument has three forms – analogical, argumentative, and prudential. None of these provides a deductive guarantee, but all can provide considerations capable of influencing the intellect. Our evaluation of such arguments reflects our background social and evaluative assumptions.

It is commonplace that negative duties are more stringent than positive duties: for example that it is harder to justify killing than letting die. It is almost equally commonplace that this distinction requires defence, in particular against those who regard it as a mere apology for the privileges of the wealthy and secure.

Despite the bad reputation of the legal profession, law remains king in America. A highly diverse society relies on the laws (and especially the Constitution) to maintain a working sense of the dignity and inviability of each individual. And a persistent element in contemporary debates is the fear that naturalistic theories of the human person will erode our belief that we have a dignity greater than that of other natural objects. Thus the endurance of the creation vs. evolution debate is due less to the arguments of creationists, or to the continued influence of the book of Genesis, than to the reading of the evidence provided by Phillip E. Johnson of the University of California, Berkeley, Law School.

Jonathan Glover and I, while not in such deep disagreement about the ethics of killing as to make all communication impossible, still disagree enough to make sustained confrontation worthwhile. (Very briefly, Glover is a utilitarian, while I am not.) At minimum, such confrontation should make it clear what are the most fundamental issues at stake in ethical arguments about various kinds of killing.

If someone abstains from meat-eating for reasons of taste or personal economics, no moral or philosophical question arises. But when a vegetarian attempts to persuade others that they, too, should adopt his diet, then what he says requires philosophical attention. While a vegetarian might argue in any number of ways, this essay will be concerned only with the argument for a vegetarian diet resting on a moral objection to the rearing and killing of animals for the human table. The vegetarian, in this laense, does not merely require us to change or justify our eating habits, but to reconsider our attitudes and behaviour towards members of other species across a wide range of practices.

The following objection to the ‘ontological’ argument of St Anselm (Proslogion II) has a continuing importance. The argument begs the question by introducing into the first premise the name ‘God’. In order for something to be truly talked about, to have properties truly attributed to it—it has been said—it must exist; a statement containing a vacuous name must either be false, meaningless, or lacking in truth-value, if it is not a misleading formulation to be explained by paraphrase into other terms. In any case the question of the divine existence is begged.

It seems clear that the ontological argument can no longer be dismissed as a silly fallacy. The dogma of the impossibility of necessary existence is seriously threatened by the case of necessary existential truths in mathematics, and as for the claim that the ontological argument must beg the question, since by mentioning God in the premise his existence is presupposed, it is undermined by the fact that we often refer to things—Hamlet for instance— we do not for a moment think exist. The doctrine that existence is not a property (‘exists’ is not a predicate), insofar as it does not reduce to one of the foregoing points, is very murky, for the sense in which ‘red’ is a predicate and ‘exists’ is not has never been clearly defined. Moreover, the way many believers hold that ‘God exists’ is immune to empirical refutation strongly suggests that we are dealing here with an analytic statement, which is just what the ontological argument should be expected to produce. It seems in order, then, to conduct theological discussion under the supposition that the argument is in fact sound.