For the ‘desire of X’ may mean the desire of it as an end (e.g. the desire of health) or as a means to an end (e.g. the desire of being doctored), or as a thing desired accidentally, as, in the case of wine, the sweet-toothed person desires it not because it is wine but because it is sweet. For essentially he desires the sweet, and only accidentally the wine: for if it be dry, he no longer desires it. His desire for it is therefore accidental.
The person who is interested in sweet wine may not be fully aware of this distinction, especially if he believes that all wine is sweet. With this belief, he may well suppose that he desires wine in itself. But he is mistaken about his own desire: his desire is for the sweet, not for wine, except accidentally.
We can make the same distinction between someone who loves truth and someone who loves an opinion for some other reason, that is, someone who loves “sweet” opinions.
As said above, if all wine were sweet, it would be easy to confuse the love of sweetness with the love of wine. A problem very close to this arises with truth and opinion: not all of a person’s beliefs are true, but as long as he believes them, he thinks that they are true. So if someone loves his beliefs, it appears to him that he loves a set of true beliefs, whether or not this is actually the case. Consequently it may appear to him that loves the truth.
But perhaps he does, and perhaps he doesn’t. He may be mistaken about his own love, just as a person can be mistaken about his desire for wine. And he may be mistaken in this way whether or not his beliefs are actually true. He may in fact love his opinions because they are “sweet”, not because they are true, and this is possible even if the beliefs are in fact true.