For whom truth exists. - … How if this effect – the effect of consolation – were precisely what truths are incapable of? – Would this then constitute an objection to truths? What have they in common with the inner states of suffering, stunted, sick human beings that they must necessarily be of use to them?...[T]ruth, as a whole and interconnectedly, exists only for souls which are at once powerful and harmless, and full of joyfulness and peace (as was the soul of Aristotle), just as it will no doubt be only such souls as these that will be capable of seeking it: for no matter how proud they may be of their intellect and its freedom, the others are seeking cures for themselves – they are not seeking truth. (Daybreak 424, trans. R.J. Hollingdale)
In this passage, Nietzsche holds up Aristotle as an example of the kind of person who is truly capable of seeking truth. This may initially strike the reader as odd, since Aristotle seems to be a systematizer of the kind that Nietzsche rails against elsewhere. But I think what Nietzsche finds admirable in Aristotle is the pursuit of truth, not for the sake of utility (however defined), but for its own sake. He speaks of the error of seeking truth for the sake of consolation, and he seems to mean both consolation in a physical sense (hence the example of the non-medicinal plant), and consolation in a more emotional sense (cf. Sextus Empiricus’ description in Outlines of Pyrrhonism I.26 of the person who is troubled by philosophical problems and seeks to resolve them satisfactorily in order to obtain some kind of contentment). But the ideal seeker after truth, according to Nietzsche, will seek truth not out of weakness or a need to be cured of bodily or mental illnesses, but out of a desire for the truth itself, apart from any benefit it may happen to bring. I think that this is why Nietzsche describes such an ideal seeker as being “powerful and harmless, and full of joyfulness and peace”.
It seems to me that the danger Nietzsche is pointing out in seeking after truth for the sake of the consolation that we think it will bring is that if we find that consolation is not in fact the result of obtaining truth, we will cease to seek after truth, and try to find consolation in some other way. If we value truth only instrumentally, then we will cease to seek after truth if we find that truth is hard or painful, or even if it is irrelevant to our need for consolation. It is only the person whom Nietzsche describes as “healthy” that can genuinely value truth.