On the doctrine that Dreams are sent from God, Books 1-2 (1.6-1.10)

Let us then at once begin and consider the first of these points. To me, then, the well appears to be an emblem of knowledge; for its nature is not superficial, but very deep. Nor does it lie in an open place, but a well is fond of being hidden somewhere in secret. Nor is it found with ease, but only after great labour and with difficulty; and this too is seen to be the case with sciences, not only with such as have great and indescribable subjects of speculation, but even with respect to such as are the most insignificant.

Choose, therefore, whichever art you please; not the most excellent, but even the most obscure of all, which perhaps no one who has been bred a free man in the whole city would ever study of his own accord, and which scarcely any servant in the field would attend to, who, against his will, was a slave to some morose and ill-tempered master who compelled him to do many unpleasant things.

For the matter will be found to be not a simple one, but rather one of great complications and variety, not easy to be seized upon, but difficult to discover, difficult to master, hostile [*] [*]

and it is owing to this that one man is more thoroughly skilled in grammar or in geometry than another, because of its being impossible to circumscribe, increase, and extend one within certain limits; for there is always more that is left behind than what comes to be learnt; and what is left watches for and catches the learner, so that even he who fancies that he has comprehended and mastered the very extremities of knowledge would be considered but half perfect by another person who was his judge, and if he were before the tribunal of truth would appear to be only beginning knowledge;

for life is short, as some one has said, but art is long; of which that man most thoroughly comprehends the magnitude, who sincerely and honestly plunges deeply into it, and who digs it out like a well. And such a man, when he is at the point of death, being now grey-headed and exceedingly old, it is said, wept, not that he feared death as being a coward, but out of a desire for instruction, as feeling that he was now, for the first time, entering upon it when he was finally departing from life.