To begin with, recall that utilitarianism is the name given to any ethical theory that says something is good if, overall, it brings about utility. This is referred to as the utility principle. Now, the utility principle can be used in different ways. The kind of utilitarian you are depends on how you use this principle.
It might seem natural for a utilitarian to be hedonic. That’s because, if you set out to increase happiness, then you probably assume that all things can be measured in terms of happiness.
But an idealist utilitarian will say that these things can’t be so easily compared. That’s because studying provides a different kind of utility than does the pleasure that comes from going out drinking. The same could be said of, for instance, the type of pleasure that comes from having a meaningful conversation with a friend, and the type of pleasure that comes from the comfort of a good bed.
But this doesn’t mean that only things that are exactly the same can be compared on the same scale.
Now, both the hedonic and idealist utilitarian can agree on an evaluation in this instance. If getting a massage brings about greater happiness, then they will both say that you should get a massage. But things get a little more complicated when we try to take into account other kinds of utility.
The idealist utilitarian says that there are some goods that are of higher value than others. For instance, the good that comes from pursuing truth for its own sake is a higher pleasure, whereas the good that comes from enjoying tasty food is a lower pleasure.
Pursuing truth doesn’t have the same enjoyment that we get immediately from eating good food. For this reason, a hedonic utilitarian may choose the latter over the former. But the idealist utilitarian sees the value in knowledge above and beyond the sensations we get from it.
Imagine you’re staying in tonight and deciding which movie you want to watch. You feel like just watching something easy and comforting, so you’re tempted by that comedy you’ve seen a dozen or more times before.
But you can’t help thinking you really should watch that difficult foreign movie that’s supposed to be intellectually challenging and rewarding.
You might have more fun watching the comedy, but the intellectual stimulation from the other movie is of a higher type.
This last example shows that two things might seem the same (i.e. two movies), but can still belong to very different scales of utility (i.e. to lower or higher pleasures) because one is closer to mere entertainment, the other to artistic or aesthetic experience.