There are valuable human activities which require the motive of money-making and the environment of private wealth-ownership for their full fruition.
 John Maynard Keynes, The General Theory of Employment, Interest and Money (1936). copy citation

Context

“for there are certain justifications for inequality of incomes which do not apply equally to inequality of inheritances. For my own part, I believe that there is social and psychological justification for significant inequalities of incomes and wealth, but not for such large disparities as exist to-day. There are valuable human activities which require the motive of money-making and the environment of private wealth-ownership for their full fruition. Moreover, dangerous human proclivities can be canalised into comparatively harmless channels by the existence of opportunities for money-making and private wealth, which, if they cannot be satisfied in this way, may find their outlet in cruelty, the reckless pursuit of personal power and authority, and other forms of self-aggrandisement.” source