In the foregoing pages the moral incentive (Compassion) has been established as a fact, and I have shown that from it alone can proceed unselfish justice and genuine loving-kindness, and that on these two cardinal virtues all the rest depend. Now, for the purpose of supplying Ethics with a foundation, this is sufficient, in a certain sense; that is, in so far as Moral Science necessarily requires to be supported by some actual and demonstrable basis, whether existing in the external world, or in the consciousness. The only alternative is to tread in the footsteps that so many of my predecessors have left, in other words, to choose arbitrarily some proposition or other, — some bare and abstract formula — and make it the source of all that morality prescribes; or, like Kant, to sublimate a mere idea, that of law, into the key-stone of the ethical arch.