The concept of need is promising and alluring because of three factors:

1. Needs are objective because it is a discoverable matter of fact what needs a person has and yet this fact has a bearing on what one ought to do. The concept is both factual and evaluative.

2. Needs are matters of priority; what we need usually overrides other reasons for action.

3. Needs are unimpeachable values. We cannot say truly that a person ought to have different needs and, in this sense, they are fundamental.

In this paper, I shall be concerned primarily with explaining the third of these features. I am interested in fundamental needs, but not necessarily basic or minimal needs, such as those pertaining to survival. Furthermore, I shall not be concerned directly in the strength of claims to need on other people, but rather on oneself. I shall use ‘need’ in such a way that the term indicates a disposition and does not imply a lack. I need food even when I am eating.

A definition of ‘need’ requires a distinction between ‘need’ and ‘desire’ and, perhaps more problematically and centrally, between fundamental and instrumental needs. An instrumental need is a necessary condition for the obtaining of a goal or for the satisfaction of a desire. To claim that X is needed instrumentally is simply to assert that X is a necessary condition for the obtaining of the contextually relevant goal, whatever that happens to be.