For these are the questions which are wont, above all, to be discussed, in any inquiry about the soul, as most important, and as best calculated to mark out its distinctive nature. And as demonstrations for the establishing of these matters of investigation, we shall employ those common modes of consideration by which the credibility of matters under hand is naturally attested. But for the purpose of brevity and utility, we shall at present make use only of those modes of argumentation which are most cogently demonstrative on the subject of our inquiry, in order that clear and intelligible notions may impart to us some readiness for meeting the gainsayers. With this, therefore, we shall commence our discussion.