This indicates also the limits of explanation. By no means every man’s reason knows when it has had enough. The less it is developed, the further is it from such knowledge. This is plainly seen in children, who often do not rest satisfied with a really satisfactory explanation. It is of first importance to be able to recognize what is a good reason. I may first say what it is _not_. It is not a _cause_. This is nothing more than a prior arrangement of the effect; the reason for an occurrence is never assigned by showing its cause. Nor is it a _caprice_, that is, motiveless volition, or will as a motor. In this sense, the “will of God” is no good reason for an occurrence. Nor is it _fate_, or physical necessity. This is denying there is any explanation to give. The reason can only be satisfied with an aliment consubstantial with itself. Nothing material like cause, nor anything incomprehensible like caprice, meets its demands. Reason is allied to order, system and purpose above all things. That which most completely answers to these will alone satisfy its requirements. They are for an ideal of order. Their complete satisfaction is obtained in universal types and measures, pure abstractions, which are not and cannot be real. The _formal law_ is the limit of explanation of phenomena, beyond which a sound intellect will ask nothing. It fulfils all the requirements of reason, and leaves nothing to be desired. Those philosophers, such as Herbert Spencer, who teach that there is some incogitable “nature” of something which is the immanent “cause” of phenomena, delude themselves with words. The history and the laws of a phenomenon _are_ its nature, and there is no chimerical something beyond them. They are exhaustive. They fully answer the question _why_, as well as the question _how_.[39-1] For it is important to note that the word “law” is not here used in the sense which Blackstone gives to it, a “rule of conduct;” nor yet in that which science assigns to it, a “physical necessity.” Law in its highest sense is the type or form, perceived by reason as that toward which phenomena tend, but which they always fail to reach. It was shown by Kant that all physical laws depend for their validity on logical laws. These are not authoritative, like the former, but purposive only. But their purpose is clear, to wit, the attainment of proportion, consistency or truth. As this purpose is reached only in the abstract form, this alone gives us the absolutely true in which reason can rest.