Which, then, of these two views is the true one? Are these two ideas merely psychological ideas in the sense which I have tried to explain, or are they not?
As I have said, I feel some doubts myself whether they are or not: it does not seem to me to be a matter to dogmatize upon. But I am strongly inclined to think that they are not merely psychological; that Moral Philosophy and Ethics are not mere departments of Psychology. In favour of the view that the two ideas in question are merely psychological, there is, so far as I am aware, nothing whatever to be said, except that so many philosophers have been absolutely convinced that they are. None of them seem to me to have succeeded in bringing forward a single argument in favour of their view. And against the view that they are, there seem to me to be some quite definite arguments, though I am not satisfied that any of these arguments are absolutely conclusive. I will try to state briefly and clearly what seem to me the main arguments against the view that these are merely psychological ideas; although, in doing so, I am faced with a certain difficulty. For though, as I have said, many philosophers are absolutely convinced, that "duty" and "good" do merely stand for psychological ideas, they are by no means agreed _what_ the psychological ideas are for which they stand. Different philosophers have hit on very different ideas as being the ideas for which they stand; and this very fact that, if they _are_ psychological ideas at all, it is so difficult to agree as to _what_ ideas they are, seems to me in itself to be an argument against the view that they are so.
Let me take each of the two ideas separately, and try to exhibit the sort of objection there seems to be to the view that it is merely a psychological idea.
Take first the idea of moral obligation. What purely psychological assertion can I be making about an action, when I assert that it was "wrong," that it ought not to have been done?
In this case, one view, which is in some ways the most plausible that can be taken, is that in every case I am merely making an assertion about my own psychology. But what assertion about my own psychology can I be making? Let us take as an example, the view of Prof. Westermarck, which is as plausible a view of this type as any that I know of. He holds that what I am judging when I judge an action to be wrong, is merely that it is of a sort which _tends_ to excite in me a peculiar kind of feeling--the feeling of moral indignation or disapproval. He does not say that what I am judging is that the action in question _is actually_ exciting this feeling in me. For it is obviously not true that, when I judge an action to be much more wrong than another, I am always actually feeling much indignation at the thought of either, or much more indignation at the thought of the one than at that of the other; and it is inconceivable that I should constantly be making so great a mistake as to my own psychology, as to think that I am actually feeling great indignation when I am not. But he thinks it is plausible to say that I am making a judgment as to the _tendency_ of such actions to excite indignation in me; that, for instance, when I judge that one is much more wrong than the other, I am merely asserting the fact, taught me by my past experience, that, if I were to witness the two actions, under similar circumstances, I should feel a much more intense indignation at the one than at the other.[1]