It is assumed, without proof, that the entire system of Being may be ranked under the three categories of Substance, Attributes, and Modes.
It is assumed, equally without proof, that there can be no substance which is not self-existent, necessary, and eternal, and that every being which does not possess these properties must be only a "mode" or affection of another being to whom they belong.

It is further assumed, also without proof, that _extension_ and _thought_ are necessary "attributes" of the one self-existent "substance," each of the two exhibiting only a different aspect of his eternal essence, while both are equally essential and equally infinite.

And, finally, it is assumed, still without proof, that Nature comprehends a twofold series of existences, distinct from each other, but developed, as it were, in parallel lines,--Corporeal and Intellectual beings, which correspond respectively to the Divine attributes of extension and thought,--which partake of the essential nature of these attributes, but exhibit them in finite and transient forms, as mere modes or manifestations of the one infinite "substance." These are some of the fundamental assumptions on which he proceeds; they are not proved, nor even attempted to be proved; for, although several are stated in the form of distinct propositions, and accompanied with a formal demonstration, the most cursory inspection of the pretended proof is sufficient to show that it consists entirely in a series of _deductions from principles previously assumed_, and that its validity must ultimately rest on the _definitions_ in which these principles are embodied.
Now, let any one examine these "definitions," and he will find that they are wholly arbitrary, and that he is not bound by any law of his intellectual nature to admit them, still less entitled, on any ground of experience, to assume and found upon them, as if they were self-evident or axiomatic truths.

It is possible, and it may even be legitimate and useful for the purposes of philosophical speculation, to classify the various objects of human knowledge by ranging them under the categories of Substance, Attributes, and Modes.

But is it a self-evident truth, that there can be no substance in nature excepting such as is self-existent and eternal?
Is it a self-evident truth that man, with his distinct personality and individual consciousness, is a mere "mode" or affection of another being?
Is it a self-evident truth that the ape, the lizard, and the worm are equally "modes" of the same substance with the angel and the seraph?
Is it a self-evident truth that _extension_ and _thought_ are equally expressive of the uncreated Essence and necessary "attributes" of the Eternal?
Is it a self-evident truth that no being can exist in nature otherwise than by _development out of the Divine substance_, and that the _creation_ of a distinct but dependent being is impossible?
In regard to questions such as these, the appeal must lie to that common sense, or those laws of thought, which are the heritage of every thinking mind, and which cannot be cramped or fettered by the arbitrary definitions of any philosophical system whatever.