sary
truth as high as we please; but they cannot give us by themselves a
single fact. I can show, for example, that a circle has an infinite
number of properties, all of which are virtually implied in the very
existence of a circle. But that the circle or that space itself exists,
is not a necessary truth, but a datum of experience. It is quite true
that such truths are not, in one sense, empirical; they can be
discovered without any change of experience; for, by their very nature,
they refer to the constant element of experience, and are true on the
supposition of the absolute changelessness of the objects contemplated.
But it is a fallacy to suppose that, because independent of particular
experiences, they are, therefore, independent of experience in general.

Now, if we agree, as Huxley would have agreed, that Hume's doctrine is
true, if we cannot know a single fact except from experience, we are
limited in moral questions, as in all others, to elaborating and
analysing our experience, and can never properly transcend it. A
scientific treatment of an ethical question, at any rate, must take for
granted all the facts of human nature. It can show what morality
actually is; what are, in fact, the motives which make men moral, and
what are the consequences of moral conduct. But it cannot get outside
of the universe and lay down moral principles independent of all
influences. I am well aware that in speaking of ethical questions upon
this ground, I am exposed to many expressions of metaphysical contempt.
I may hope to throw light upon the usual working of morality; but my
theory of the facts cannot make men moral of itself. I cannot hope, for
example, to show that immorality involves a contradiction, for I know
that immorality exists. I cannot even hope to show that it is
necessarily productive of misery to the individual, for I know that
some people take pleasure in vicious conduct. I cannot deduce facts
from morals, for I must consistently regard morals as part of the
observed consequences of human nature under given conditions.
Metaphysicians may, if they can, show me a more excellent method. I
admit that their language sometimes enables them to take what, in words
at least, is a sublimer position than mine. Kant's famous phrase, "Thou
must, therefore thou canst," is impressive. And yet, it seems to me to
involve an obvious piece of logical juggling. It is quite true that
whenever it is my duty to act in a certain way,