Perhaps, as it seems, [Celsus] did not understand the doctrine that Jesus was a man [in addition to being divine], and did not want him to have any human experience, nor to become a noble example to men to show them how to bear calamities. This seems to Celsus to be just lamentable and reprehensible, since [being an Epicurean] he regards pain as the greatest evil and pleasure as the greatest good, although this view is accepted by no philosopher among those who believe in providence and admit that courage, bravery, and noble-mindedness are virtues (Contra Celsum II:42).Notice what Origen says: no philosopher who admits the existence of providence (i.e. who believes that the events of history are foreseen and ordered by God) thinks that the greatest evil is pain and the greatest good is pleasure. No one who believes that all things are ordered and foreknown by God, in other words, measures all value and worth by reference to the pleasure or pain produced by a thing. Now why is that?
The line of reasoning which suggests itself to me is the following. Experiencing life in the world tells us that whoever ordered the events of history does not primarily care about giving us as much pleasure and as little pain as possible. On the contrary, evil things happen to good people and good things happen to evil people; some enjoy themselves for some period of time while others suffer seemingly uninterruptedly. The arrangement of the world, in other words, doesn't reflect the thought of a person who values pleasure above everything else and detests pain the most.
One might ponder this fact and come to the conclusion that there is no providence, since pleasure is the greatest good and pain the greatest evil. This is Epicurean atheism of the sort that Celsus believed, and which is believed by very many people these days, too. Origen suggests that it is hard to justify a morally robust sense of virtue on this scheme of things. On the other hand, one might observe the arrangement of the world and conclude that some other things besides pleasure and pain must be the moral ultimates. This is Christianity and other philosophical views like Stoicism and Platonism, etc.
The practical upside of this discussion is the following: we ought to keep a close watch on our thinking and values, lest an obsession with pleasure should turn us against God when things turn out painful for us, as they inevitably will. And we ought to beware of social trends and currents of thought which seem motivated by an amoral aversion to pain at any cost.
An example from my current experience: there are parenting trends becoming increasingly popular here in Romania which speak against any discipline or moral evaluation of children at all. You should not punish your children or correct them—so the argument goes—because this causes the child to experience distress, and at the end of the day, what the child is doing is not a big deal anyway. Neither should children be given grades or evaluated at school, etc. Behind these very much non-traditional suggestions is a certain philosophy, one which evidently seeks to avoid pain at any cost as the ultimate evil. But the truth is that only through pain can any progress be made, including moral progress. Unless you push your limits, you will never increase in athleticism and fitness. Unless you make an effort to do the right thing when it is difficult, and when your strongest desires are against it, you will never make moral progress. Pain and distress are the means by which progress is made; that is why providence permits them, because feeling pain is not worse than being morally bankrupt and vicious.
So also, the fact that Christ suffered greatly in the body for the sake of human salvation shows, as Origen writes, that providence considers other things besides pleasure and pain to be moral ultimates.