As regards the uncertainty about everything which Varro alleges to be the differentiating characteristic of the New Academy, the city of God thoroughly detests such doubt as madness. Regarding matters which it apprehends by the mind and reason it has most absolute certainty, although its knowledge is limited because of the corruptible body pressing down the mind, for, as the apostle says, "We know in part."[650] It believes also the evidence of the senses which the mind uses by aid of the body; for [if one who trusts his senses is sometimes deceived], he is more wretchedly deceived who fancies he should never trust them. It believes also the Holy Scriptures, old and new, which we call canonical, and which are the source of the faith by which the just lives,[651] and by which we walk without doubting whilst we are absent from the Lord.[652] So long as this faith remains inviolate and firm, we may without blame entertain doubts regarding some things which we have neither perceived by sense nor by reason, and which have not been revealed to us by the canonical Scriptures, nor come to our knowledge through witnesses whom it is absurd to disbelieve. 19. _Of the dress and habits of the Christian people._ It is a matter of no moment in the city of God whether he who adopts the faith that brings men to God adopts it in one dress and manner of life or another, so long only as he lives in conformity with the commandments of God. And hence, when philosophers themselves become Christians, they are compelled, indeed, to abandon their erroneous doctrines, but not their dress and mode of living, which are no obstacle to religion. So that we make no account of that distinction of sects which Varro adduced in connection with the Cynic school, provided always nothing indecent or self-indulgent is retained. As to these three modes of life, the contemplative, the active, and the composite, although, so long as a man's faith is preserved, he may choose any of them without detriment to his eternal interests, yet he must never overlook the claims of truth and duty. No man has a right to lead such a life of contemplation as to forget in his own ease the service due to his neighbour; nor has any man a right to be so immersed in active life as to neglect the contemplation of God. The charm of leisure must not be indolent vacancy of mind, but the investigation or discovery of truth, that thus every man may make solid attainments without grudging that others do the same. And, in active life, it is not the honours or power of this life we should covet, since all things under the sun are vanity, but we should aim at using our position and influence, if these have been honourably attained, for the welfare of those who are under us, in the way we have already explained.[653] It is to this the apostle refers when he says, "He that desireth the episcopate desireth a good work."[654] He wished to show that the episcopate is the title of a work, not of an honour.