… is from page 19 of James Gwartney’s and the late Richard Stroup’s splendid 1993 primer, What Everyone Should Know About Economics and Prosperity:
Income is simply compensation received in exchange for productive services supplied to others. People who earn large incomes provide others with lot of things that they value. If they did not, other people would not be willing to pay them so generously. There is a moral here. If you want to earn a large income, you had better figure out how to help others a great deal. The converse is also true. If you are unable and unwilling to help others very much, your income will be quite small.
DBx: Yep. To tax income, therefore, is to tax the help we give to others.