As, therefore, some of those who have dug wells have often done so without finding water; so likewise those who advance far in knowledge, and who have made great progress in it, are still often unable to attain to the end which they desire. At all events, they say that men of extensive learning often find fault with their terrible ignorance, for they only just know how far they are removed from the truth. And there is a story that some man of old time, when he was admired for his wisdom, said, that it was a fine thing that he should be admired, who only just knew that he knows nothing.
 And choose, if you like, any art you please, whether trifling or important, and the man, too, who is most excellent, and most highly thought of in regard of his skill in it,
 Genesis xxvi. 32. 
 
and then consider if the professions held out by the art are equal to the performances of the artist; for if you duly examine the matter, you will find that the performance falls short of the profession, not by a small, but by a vast distance, it being almost impossible for a man to be perfect in any art whatever, which is in continual motion like a fountain, and is constantly pouring forth various species of all kinds of speculations.