For Galbraith, historical social darwinism, 1980s supply side theory, current efforts to revive supply side policy, and efforts to reduce welfare, are based on faulty assumptions about human motivation. Supply side theory and current welfare arrangements assume different motivations at the top and bottom of society, that the rich do not work hard enough because they have insufficient rewards (incentives) and that the poor do not work hard enough because minimum wage laws and welfare systems give them too much, discouraging effort. This, of course, implies that the rich are not doing their job, that their performance is bad and inadequate. For Galbraith, this suggests that they may need higher, not lower, taxes to encourage their effort, "in order to sustain their after-tax income."

http://plsc.uark.edu/584v/critique.htm