If any one affirms (says Spinoza) that he has a clear, distinct--that is to say, a true--idea of substance, but that nevertheless he is uncertain whether any such substance exist, it is the same as if he were to affirm that he had a true idea, but yet was uncertain whether it was not false. Or if he says that substance can be created, it is like saying that a false idea can become a true idea--as absurd a thing as it is possible to conceive; and therefore the existence of substance, as well as the essence of it, must be acknowledged as an eternal verity. It is again the same story. Spinoza speaks of a clear idea of substance; but he has not proved that such an idea is within the compass of the mind. A man's own notion that he sees clearly, is no proof that he really sees clearly; and the distinctness of a definition in itself is no evidence that it corresponds adequately with the object of it. No doubt a man who professes to have an idea of substance as an existing thing, cannot doubt, as long as he has it, that substance so exists. This is merely to say that as long as a man is certain of this or that fact, he has no doubt of it. But neither his certainty nor Spinoza's will be of any use to a man who has no such idea, and who cannot recognise the lawfulness of the method by which it is arrived at. From the self-existing substance it is a short step to the existence of God. After a few more propositions, following one another with the same kind of coherence, we arrive successively at the conclusion that there is but one substance; that this substance being necessarily existent, it is also infinite; that it is therefore identical with the Being who had been previously defined as the 'Ens absolute perfectum.' Demonstrations of this kind were the characteristics of the period. Des Cartes had set the example of constructing them, and was followed by Cudworth, Clarke, Berkeley, and many others besides Spinoza. The inconclusiveness of the method may perhaps be observed most readily in the strangely opposite conceptions formed by all these writers of the nature of that Being whose existence they nevertheless agreed, by the same process, to gather each out of their ideas. It is important, however, to examine it carefully, for it is the very keystone of the Pantheistic system. As stated by Des Cartes, the argument stands something as follows:--God is an all-perfect Being,--perfection is the idea which we form of Him: existence is a mode of perfection, and therefore God exists. The sophism we are told is only apparent. Existence is part of the idea--as much involved in it as the equality of all lines drawn from the centre to the circumference of a circle is involved in the idea of a circle. A non-existent all-perfect Being is as inconceivable as a quadrilateral triangle.