Now, the question arises--'Can such an objectivity be asserted by those who take a purely materialistic or naturalistic view of the Universe?' Whatever our metaphysical theories about the nature of Reality may be, we can in practice have no difficulty in the region of Physical Science about recognizing an objective reality of some kind which is other than my mere thinking about it. That fire will burn whether I think so or not is practically recognized by persons of all metaphysical persuasions. If I say 'I can cloy the hungry edge of appetite by bare imagination of a feast,' I try the experiment, and I fail. I imagine the feast, but I am hungry still: and if I persist in the experiment, I die. But what do we mean when we say that things are right or wrong whether I think them so or not, that the Moral Law exists outside me and independently of my thinking about it? Where and how does this moral law exist? The physical laws of Nature may be supposed by the Materialist or the Realist somehow to exist in matter: to the Metaphysician there may be difficulties in such a view, but the difficulties are not obvious to common-sense. But surely (whatever may be thought about physical laws) the moral law, {74} which expresses not any matter of physical fact but what _ought_ to be thought of acts, cannot be supposed to exist in a purely material Universe. An 'ought' can exist only in and for a mind. In what mind, then, does the moral law exist? As a matter of fact, different people's moral judgements contradict one another. And the consciousness of no living man can well be supposed to be a flawless reflection of the absolute moral ideal. On a non-theistic view of the Universe, then, the moral law cannot well be thought of as having any actual existence. The objective validity of the moral law can indeed be and no doubt is _asserted_, believed in, acted upon without reference to any theological creed; but it cannot be defended or fully justified without the pre-supposition of Theism. What we mean by an objective law is that the moral law is a part of the ultimate nature of things, on a level with the laws of physical nature, and it cannot be _that_, unless we assume that law to be an expression of the same mind in which physical laws originate. The idea of duty, when analysed, implies the idea of God. Whatever else Plato meant by the 'idea of the good,' this at least was one of his meanings--that the moral law has its source in the source of all Reality.