All skill ought to be exerted for universal good; every man has owed much to others, and ought to repay the kindness that he has received.
 Samuel Johnson, The History of Rasselas, Prince of Abissinia (1759). copy citation

Context

“But I will work only on this condition, that the art shall not be divulged, and that you shall not require me to make wings for any but ourselves. ” “ Why, ” said Rasselas, “ should you envy others so great an advantage? All skill ought to be exerted for universal good; every man has owed much to others, and ought to repay the kindness that he has received. “ If men were all virtuous, ” returned the artist, “ I should with great alacrity teach them to fly. But what would be the security of the good if the bad could at pleasure invade them from the sky? Against an army sailing through the clouds neither walls, mountains, nor seas could afford security.” source