The justification of a wholly non-Humean conceptual scheme, based upon the idea of enduring individuals with powers, rests in part on the success of such a scheme in resolving the problems bequeathed to us by the Humean tradition and in part must be achieved by a careful construction of the metaphysics of the new scheme itself. By this we mean a thorough exposition of the meaning and interrelations of the concepts of the new scheme. It is to the latter task that we turn in this paper, being satisfied that the power of the scheme to give a rational account of science has been shown, and that its effectiveness in resolving the Humean problems and dilemmas has been amply demonstrated.

In Chapter VI of his powerful study God and Other Minds Dr Alvin Plantinga deploys what—following a suggestion of mine—he calls ‘The Free Will Defence’. He presents his case there as a reaction to two earlier attempts to overcome that defence. I propose to take this chapter in Plantinga as my starting point here; and, as far as can be, to ignore, though not by that token to repudiate, those by now rather ancient earlier essays.

1. The scientific study of sleep has recently been stimulated by comparisons between people and advanced computers, whose normal activities need to be suspended periodically for reprogramming. I quote from a popular account by Dr Christopher Evans, which appeared in the Sunday Times during 1969:

Sleep is of course the state in which the brain-computer is ‘off-line’, during which time the vast mass of existing programmes are sorted, outdated ones revised in the light of recent experiences and useless ones or the remnants of modified ones cleared and eliminated. These processes take place for a substantial part of the night, but because the brain is ‘off-line’ and consciousness suppressed, we are mostly not aware of them. However, if for some reason our sleep is disturbed or when we wake in the morning, as the conscious mind ‘comes to’ it catches the programme operations at work, and for a moment has no way of knowing whether the events are internal or external in origin. It sets to work therefore to try to make sense of the programme or fragments thereof that are being run through, and the result is what we call a dream— though we should presumably call it an interrupted dream.

In Book IV of The Odyssey, Menelaus tells Telemachus as much as he knows of Odysseus' wanderings. He reports that Odysseus, wanting to learn the end of his travels and needing directions for returning safely home through the dangerous seas, captured Proteus and held fast to him, though Proteus transformed himself into a bearded lion, a snake, a leopard, a bear, running water and finally into a flowering tree. Proteus eventually wearied, and consented to tell Odysseus something of what he wished to know.

The reappearance of Professor Alasdair MacIntyre's far-ranging and provocative article, ‘Hume on “is” and “ought”’, is the proximate cause of this short excursion to an old, well-scarred, and still fascinating battleground. Re-reading MacIntyre's brilliant offensive thrust led me to review the counter-attacks and diversionary movements that followed its first appearance. They in turn sent me back, inevitably and ultimately, to look again at the cause of this philosophic skirmishing: Section 1 of Part i of Book III of Hume's Treatise of Human Nature, entitled ‘Moral Distinctions not deriv'd from Reason’. The battles of the past have been waged chiefly round the last paragraph of this Section (pp. 469–470 in Selby-Bigge's edition), but my primary concern here is going to be with those ‘reasonings’ that precede the celebrated ‘is-ought’ paragraph. Closer attention to the bulk of Book III, Part i, Section 1, to which ‘reasonings’ Hume says he ‘cannot forbear adding … an observation’ on ‘is’ and ‘ought’, and some selective attention as well to Books I and II of the Treatise, should help to scale down the exaggerated importance attached to the ‘is-ought’ passage. Unless this is done, one runs the risk of permitting a tailpiece to wag the body of the chapter, if not the whole Book ‘Of Morals’.

In one way or another the theory and practice of modern medicine is confronting us with many dilemmas, chiefly, though not exclusively, of a moral character; the transplantation of organs, abortion, and euthanasia are examples, and closely associated with these are more obviously conceptual problems such as the definition of death and, for that matter, of life itself. Contemporary moral philosophers have been strangely silent on these matters, and have been content to leave the field to lawyers and churchmen and those few medical men both able and willing to reflect upon their practices. (I think it is fair to say that the attitude of the profession as a whole is exemplified by the physician who recently dismissed a journalist's question about how he decided which patients were to receive kidney dialysis and which not, with the remark ‘I'm not a moralist, I'm a doctor’.)

For a long time Hume's philosophical achievement was judged almost entirely by Book I of the Treatise. A major contribution of Kemp Smith's work on Hume was the insistence that the epistemological doctrines of Book I were essentially related to the ethical theory of Book III. Recent moral philosophy has found Book III to be of considerable intrinsic interest and relevance to current problems. It is now becoming apparent, however, that Hume's ethical theory is intimately bound up with the philosophy of mind in Book II. This new emphasis upon the significance of Book II for Hume's ethics derives from Dr Pall S. Árdal's book Passion and Value in Hume's Treatise. In view of Árdal's influence on continuing study in this field—witness the recent book by Philip Mercer—it becomes important to point out what I take to be a major error in one part of Árdal's analysis of the relationship between Hume's philosophy of mind and his moral theory.

Christopher Cherry's article in the January 1973 issue of this journal has on its first page the sentence ‘And when a philosopher writes that “no clear idea is available to us of what moral scepticism amounts to”, that moral scepticism would, if it were possible at all, have to be a “specially cooked-up affair” by contrast with other varieties of scepticism, it is hard not to accuse him of just such a vice.’ He means the vice of disingenuousness and the person to whom he attributes it is me. I did not write what he says I wrote and neither of his quotations is accurate. On the next page Cherry claims again to be summarizing a view of mine when he says that ‘An “intellectual moral scepticism” would, if it were anything, have to be a peculiarly cooked-up affair, and so by implication different from other forms of intellectual philosophical scepticism. It is not a species of the same genus.’