More of the Abolition of Man by C.S. Lewis - instincts?

But why ought we to obey Instinct? Is there another instinct of a higher order directing us to do so, and a third of a still higher order directing us to obey it?—an infinite regress of instincts? This is presumably impossible, but nothing else will serve. From the statement about psychological fact 'I have an impulse to do so and so' we cannot by any ingenuity derive the practical principle 'I ought to obey this impulse'. Even if it were true that men had a spontaneous, unreflective impulse to sacrifice their own lives for the preservation of their fellows, it remains a quite separate question whether this is an impulse they should control or one they should indulge. For even the Innovator admits that many impulses (those which conflict with the preservation of the species) have to be controlled. And this admission surely introduces us to a yet more fundamental difficulty.

Telling us to obey Instinct is like telling us to obey 'people'. People say different things: so do instincts. Our instincts are at war. If it is held that the instinct for preserving the species should always be obeyed at the expense of other instincts, whence do we derive this rule of precedence? To listen to that instinct speaking in its own cause and deciding it in its own favour would be rather simple-minded. Each instinct, if you listen to it, will claim to be gratified at the expense of all the rest. By the very act of listening to one rather than to others we have already prejudged the case. If we did not bring to the examination of our instincts a knowledge of their comparative dignity we could never learn it from them. And that knowledge cannot itself be instinctive: the judge cannot be one of the parties judged; or, if he is, the decision is worthless and there is no ground for placing the preservation of the species above self-preservation or sexual appetite.

The idea that, without appealing to any court higher than the instincts themselves, we can yet find grounds for preferring one instinct above its fellows dies very hard. We grasp at useless words: we call it the 'basic', or 'fundamental', or 'primal', or 'deepest' instinct. It is of no avail. Either these words conceal a value judgement passed upon the instinct and therefore not derivable from it, or else they merely record its felt intensity, the frequency of its operation and its wide distribution. If the former, the whole attempt to base value upon instinct has been abandoned: if the latter, these observations about the quantitative aspects of a psychological event lead to no practical conclusion. It is the old dilemma. Either the premisses already concealed an imperative or the conclusion remains merely in the indicative.³