The characteristic of the purely speculative portion of Platonism is the theory of _ideas_ (used by the author in the new sense of _unities_, the original meaning being _forms_ and _figures_), of which it may be said that its merit depends upon its poetic fancy rather than upon its scientific value. Divesting it of the verbiage of the commentators, who have not succeeded in making it more intelligible, all that need be said of this abstruse and fantastic notion is, that by it he intended to convey that all sensible objects which, according to him, are but the shadows and phantoms of things unseen, are ultimately referable to certain abstract conceptions or ideas, which he termed _unities_, that can only be reached by pure thinking. Hence he asserted that “not being in a condition to grasp the idea of the Good with full distinctness, we are able to approximate to it only so far as we elevate the power of thinking to its proper purity.” Whatever may be thought of the premiss, the truth and utility of the deduction may be allowed to be as unquestionable as they are unheeded. This characteristic theory may be traced to the belief of Plato not only in the immortality, but also in the past eternity of the soul. In the _Phædrus_, under the form of allegory, he describes the soul in its former state of existence as traversing the circuit of the universe where, if reason duly control the appetite, it is initiated, as it were, into the essences of things which are there disclosed to its gaze. And it is this ante-natal experience, which supplies the fleshly mind or soul with its ideas of the beautiful and the true.