All the possible properties of a circle may be deduced from the simple definition of it; but it will not follow that all the possible forms of being in nature may be deduced from the definition of "substance." The reason is clear; we cannot have such a definition of substance as we may have of a circle.

We do not object merely to the _geometrical form_ of his reasoning,--that is a mere accessory, and one which renders the "Ethica" much more dry and less attractive than the "Tractatus," in which he gives free scope to his subtle intellect, unfettered by any such artificial plan,--but we object to the essential nature of his system, to the _a priori_ and deductive method by which he attempts to solve some of the highest problems of philosophy respecting God, Nature, and Man.

Here, if anywhere, is a field of inquiry which demands for its due cultivation an enlarged experience and a patient spirit of induction.

Yet, with him, the starting-point of philosophy is the highest object of human thought.

He begins with the idea of self-existent Being, without which, as he imagines, nothing else can be conceived; and then, following the line of a descending series, he attempts to deduce from it the philosophy of the whole system of the universe![124] His Metaphysics must borrow nothing from experience; his very Psychology must be purely deductive.
From the intuitive idea of "substance" he deduces the nature and existence of God; from the nature of God, the necessity of a Divine development; from the necessity of a Divine development, the existence of a universe comprising souls and bodies; and nowhere does he condescend to take notice of the facts of experience, except in two of his axioms, in which he assumes that "man thinks," and that "he feels his body to be affected in various ways." His whole philosophy resolves itself ultimately into an intellectual intuition, whose object is Substance or Being, with its infinite attributes of extension and thought,--an intuition which discerns its object directly and immediately, in the light of its own self-evidence, without the aid of any intermediate sign, and which is as superior, in a philosophical point of view, to the intimations of sense, as its objects are superior to the fleeting phenomena of Nature.
Now, we submit that this method of constructing a philosophy of Nature is radically vicious, and diametrically opposed to the only legitimate, the only possible way of attaining to sound knowledge.