Chapter IV.—Summary of the Opinions of Philosophers Continued. Persuaded, then, that the principle of physiology is confessedly discovered to be encumbered with difficulties for all these philosophers, we ourselves also shall fearlessly declare concerning the examples of the truth, as to how they are, and as we have felt confident that they are . But we shall previously furnish an explanation, in the way of epitome, of the tenets of the heresiarchs, in order that, by our having set before our readers the tenets of all made well known by this (plan of treatment), we may exhibit the truth in a plain and familiar (form).