The Republic by Plato Part 2 Page 55

in order that we might have our shoes well made; but to him and to every other worker was assigned one work for which he was by nature fitted, and at that he was to continue working all his life long and at no other; he was not to let opportunities slip, and then he would become a good workman. Now nothing can be more important than that the work of a soldier should be well done. But is war an art so easily acquired that a man may be a warrior who is also a husbandman, or shoemaker, or other artisan; although no one in the world would be a good dice or draught player who merely took up the game as a recreation, and had not from his earliest years devoted himself to this and nothing else?

No tools will make a man a skilled workman, or master of defence, nor be of any use to him who has not learned how to handle them, and