For, in fine, it is impossible that the immutable should assume firmness and consistency in the mutable. But the ruling faculty being in perpetual change, and therefore unstable, the force of habit is not maintained. For how can he who is perpetually changed by external occurrences and accidents, ever possess habit and disposition, and in word, grasp of scientific knowledge (ἐριστήμη)? Further, also, the philosophers regard the virtues as habits, dispositions, and sciences. And as knowledge (_gnosis_) is not born with men, but is acquired,[1026] and the acquiring of it in its elements demands application, and training, and progress; and then from incessant practice it passes into a habit; so, when perfected in the mystic habit, it abides, being infallible through love. For not only has he apprehended the first Cause, and the Cause produced by it, and is sure about them, possessing firmly firm and irrefragable and immoveable reasons; but also respecting what is good and what is evil, and respecting all production, and to speak comprehensively, respecting all about which the Lord has spoken, he has learned, from the truth itself, the most exact truth from the foundation of the world to the end. Not preferring to the truth itself what appears plausible, or, according to Hellenic reasoning, necessary; but what has been spoken by the Lord he accepts as clear and evident, though concealed from others; and he has already received the knowledge of all things. And the oracles we possess give their utterances respecting what exists, as it is; and respecting what is future, as it shall be; and respecting what is past, as it was. In scientific matters, as being alone possessed of scientific knowledge, he will hold the pre-eminence, and will discourse on the discussion respecting the good, ever intent on intellectual objects, tracing out his procedure in human affairs from the archetypes above; as navigators direct the ship according to the star; prepared to hold himself in readiness for every suitable action; accustomed to despise all difficulties and dangers when it is necessary to undergo them; never doing anything precipitate or incongruous either to himself or the common weal; foreseeing; and inflexible by pleasures both of waking hours and of dreams. For, accustomed to spare living and frugality, he is moderate, active, and grave; requiring few necessaries for life; occupying himself with nothing superfluous. But desiring not even these things as chief, but by reason of fellowship in life, as necessary for his sojourn in life, as far as necessary. CHAPTER X. THE GNOSTIC AVAILS HIMSELF OF THE HELP OF ALL HUMAN KNOWLEDGE.