We are too feeble and sluggish to make our way out to the upper limit of the air. If someone could reach the summit, or put on wings and fly aloft, when he put up his head he would see the world above, just as fishes see our world when they put up their heads out of the sea; and if his nature were able to bear the sight, he would recognize that that is the true heaven.
PlatoWhat the expression is intended to mean, I think, is that there is a better and a worse element in the character of each individual, and that when the naturally better element controls the worse then the man is said to be "master of himself", as a term of praise. But when - as a result of bad upbringing or bad company one s better element is overpowered by the numerical superiority of one s worse impulses, then one is criticized for not being master of oneself and for lack of self control.
Plato