It is clear that in speaking of thought and the thinking subject, we cannot forget experience, since it is impossible to abstract the basis of all psychological investigations,--_I think_,--a proposition which expresses a fact of consciousness, an act of internal experience; but with this experience is combined the idea of unity in general, or the exclusion of distinction and multiplicity from the act of thought and from the thinking subject. Thus the demonstration of the simplicity of the soul follows in the same path as all demonstrations which are confined to the purely ideal order, and which consequently are formed of one premise which contains a necessary truth, and another which establishes a fact of experience. In the present instance, the necessary premise is the very definition of unity and simplicity; the other expresses the fact experienced, that is, the nature of the thought, as it is revealed in consciousness. 88. Hence the demonstration of the simplicity of thinking beings is not limited to the human mind, but extends to all the subjects in which the fact of consciousness exists. When Kant says we cannot extend this demonstration, because we then go out of the field of experience, we reply with this argument: our demonstration is founded on the idea of unity and the fact of consciousness; the idea of unity is general, and consequently is valid in all cases; the fact of consciousness is a thing which is found in every thinking being, since thought is inconceivable without a subject, which may say, _I think_; therefore, we proceed legitimately in extending the demonstration of simplicity, unless you mean to give to the word _think_ a very different meaning from that which we all give to it, in which case we go out of the arena of philosophy and enter on a discussion of words.