A trivial good may, from certain circumstances, produce a desire superior to what arises from the greatest and most valuable enjoyment; nor is there any thing more extraordinary in this, than in mechanics to see one pound weight raise up a hundred by the advantage of its situation.

In short, a passion must be accompanyed with some false judgment in order to its being unreasonable; and even then it is not the passion, properly speaking, which is unreasonable, but the judgment.
The consequences are evident.

Since a passion can never, in any sense, be called unreasonable, but when founded on a false supposition or when it chuses means insufficient for the designed end, it is impossible, that reason and passion can ever oppose each other, or dispute for the government of the will and actions.

The moment we perceive the falshood of any supposition, or the insufficiency of any means our passions yield to our reason without any opposition.

I may desire any fruit as of an excellent relish; but whenever you convince me of my mistake, my longing ceases.