This topic was raised in reading Bernard Williams, in “Internal and External Reasons” (in Moral Luck, Cambridge: Cambridge University Press, 1981, 101–13). However, he mentioned it briefly so, in effect, he only raised the topic.
I shall not try to discuss here the nature of needs, but I take it that insofar as there are determinately recognizable needs, there can be an agent who lacks any interest in getting what he indeed needs. I take it, further, that the lack of interest can remain after deliberation, and, also, that it would be wrong to say that such a lack of interest must always rest on false beliefs.
Unlike Williams, I am going to say something about the nature of needs.
Remember, I am using this blog as a place to store notes on things that I am reading. A proper accounting of "needs" will require a lot more reading. This series of blog postings has already taken one side track (from a discussion of J.L. Mackie's error theory to a discussion of internal and external reasons) and then a second (a discussion of internal and external reasons to a discussion specifically of Bernard Williams' paper on that topic). I am trying to avoid yet another side track in the hopes of returning to the original discussion.
This, then, transfers the reason to acquire what is needed from the reason to acquire S. If the agent loses the reason to acquire S, then the agent loses the need for N.
This account of needs is not the same that Williams is willing to take. An agent who has no means-interest in getting what he needs in fact must be unaware of the relationship between N and S.
Later, Williams spoke of a person who needed medication in order to realize some health state S. In this state, it may well be true that the agent needs the medication in order to reach a particular state of health. However, we may be wrong in saying that the agent has a reason to achieve that particular state of health. In this case, the agent also lacks reasons to take the medication. This describes a way in which an agent may “need” something, and have no interest in obtaining it even after deliberation, and his lack of interest does not rest on a false belief. It rests on having a reason to reach the assigned end.
Such an agent can well say, “Yes, it is true that a person needs to take the medicine in order to reach health state S, but I have no interest in health state S; therefore, I have no reason to take the medicine.” This agent can also just as easily say, “I don’t need the medicine. Give it to those who do.”
It still seems to be the case, at least to me, that the discussion could benefit from more carefully distinguishing between means and ends. The question of whether the concept of “needs” supports the concept of “external reasons” or can be handled by a theory of “internal reasons” seems to be precisely the question of whether it is true that “needs” can always be expressed in the form of “in order to S, Agent needs N”, where the reasons to acquire N are fully dependent on the (internal) reasons to acquire S. An external reasons theorist may disagree with this, but this seems to be where the debate lies.