Morality and reason

Let us suppose for a moment that the harder virtues could really be theoretically justified with no appeal to objective value. It still remains true that no justification of virtue will enable a man to be virtuous. Without the aid of trained emotions the intellect is powerless against the animal organism. I had sooner play cards against a man who was quite skeptical about ethics, but bred to believe that "a gentleman does not cheat," than against an irreproachable moral philosopher who had been brought up among sharpers. In battle it is not syllogisms that will keep the reluctant nerves and muscles to their post in the third hour of the bombardment. The crudest sentimentalism… about a flag or a country or a regiment will be of more use.

C.S.Lewis,
in The Abolition of Man

This book is quite complex, and any quotation threatens to be misinterpreted as out of context. The entire book is the context. It’s short and hard to isolate aphorisms. Anyway, the "trained emotions" he is referring to is traditional values. He is testifying (I think) to the importance of having been taught independently moral principles. He is making the case for teaching sentimentalism. Teaching children patriotism. Teaching morality. He makes the interesting case that without natural moral law, there can be no valid arguments to create morality through reason.

The Innovator is trying to get a conclusion in the imperative mood out of premises in the indicative mood: and though he continues trying to all eternity he cannot succeed, for the thing is impossible. We must therefore either extend the word Reason to include what our ancestors called Practical Reason and confess that judgements such as society ought to be preserved …are not mere sentiments but are rationality itself: or else we must give up at once, and for ever, the attempt to find a core of "rational" value behind all the sentiments we have debunked.