2. The doctrine of "Identity" constitutes a prominent and indispensable part of the theory of Idealism, and is the ground-principle of Philosophical Pantheism. It amounts, in substance, to the proposition, that Existence and Thought are _one_, that the "subject" and "object" of knowledge are _one_. "If the doctrine of Identity means anything, it means that Thought and Being are essentially one; that the process of _thinking_ is virtually the same as the process of _creating_; that in constructing the universe by logical deduction, we do virtually the same thing as Deity accomplishes in developing himself in all the forms and regions of creation; that every man's reason, therefore, is really God; in fine, that Deity is the whole sum of consciousness immanent in the world."[137] It is through the medium of this doctrine of Identity that Idealism passes into Pantheism,--not, indeed, the Idealism of Berkeley, which recognized, consistently or otherwise, the existence of the human mind and of the Divine Spirit, while it denied the independent existence of matter,--but the Idealism of Fichte and others, which resolved mind into a mere process of thought, a continuous stream or succession of ideas. To _such_ a theory the doctrine of Identity was indispensable. Its advocates were bound to show that nothing existed, or could be proved to exist, in the universe but _thought_, and that, in every case, the _subject_ and _object_ of thought might be identified as one. We find, accordingly, that from the earliest ages down to the present time, the idea of "absolute unity," or "universal identity," has been frequently exhibited in connection with the speculations of philosophical Idealists. The disciples of the Eleatic school in ancient Greece, not less than those of the modern schools of Germany, insisted on the identity of thought and its object, and regarded everything that might seem to be external to the mind as a mere illusion.