  A good place to start is with the question whether claims of the form ‘\(A\) needs \(X\)’ are always elliptical, that is whether they are always opaque unless filled out by supplying the end, \(Y\), for which \(X\) is needed. Clearly many need statements have that property. If I say ‘Mary needs a hat’, then unless the context makes it clear already, it is apposite to ask ‘What does she need the hat for?’ to which the answer might be ‘To avoid getting sunburnt’. Yet other need claims seem not to be elliptical in that way. If I say ‘the baby needs its diaper changed’, it would be more than a little bizarre to ask ‘what for?’. Although it would no doubt be possible formally to expand the sentence by specifying a goal, no fresh information would be supplied to anyone who already knew what a baby was and what a diaper was, whereas in the case of Mary’s hat, the reference to sunburn does genuine explanatory work by displacing other reasons that Mary might have for needing suitable headgear.