Something is needed for some end if the end cannot be achieved without it. If living things are thought of as having a set of real or true ends, as in Aristotelian teleological accounts of human beings, then their real or true needs will be whatever is required for those ends to be achieved. The meeting of needs can then be the foundation of an ethic. The difficulty is to shake the idea loose from its Aristotelian underpinnings. Without those, the idea of a need is apt to dilute into the idea of an interest or a desire. See also capabilities.