The Divine Institutes

For there are many things which nature itself, and frequent use, and the necessity of life, compel us to know. Accordingly you must perish, unless you know what things are useful for life, in order that you may seek them; and what are dangerous, that you may shun and avoid them. Moreover, there are many things which experience finds out. For the various courses of the sun and moon, and the motions of the stars, and the computation of times, have been discovered, and the nature of bodies, and the strength of herbs by students of medicine, and by the cultivators of the land the nature of soils, and signs of future rains and tempests have been collected.

In short, there is no art which is not dependent on knowledge. Therefore Arcesilas ought, if he had any wisdom, to have distinguished the things which were capable of being known, and those which were incapable. But if he had done this, he would have reduced himself to the common herd. For the common people have sometimes more wisdom, because they are only so far wise as is necessary. And if you inquire of them whether they know anything or nothing, they will say that they know the things which they know, and will confess that they are ignorant of what they are ignorant.

He was right, therefore, in taking away the systems of others, but he was not right in laying the foundations of his own. For ignorance of all things cannot be wisdom, the peculiar property of which is knowledge. And thus, when he overcame the philosophers, and taught that they knew nothing, he himself also lost the name of philosopher, because his system is to know nothing. For he who blames others because they are ignorant, ought himself to have knowledge; but when he knows nothing, what perverseness or what insolence it is, to constitute himself a philosopher on account of that very thing for which he takes away the others!

For it is in their power to answer thus: If you convict us of knowing nothing, and therefore of being unwise because we know nothing, does it follow that you are not wise, because you confess that you know nothing? What progress, therefore, did Arcesilas make, except that, having dispatched all the philosophers, he pierced himself also with the same sword?