Toward the beginning of the Philebus (“On Pleasure”) we get the following exchange:
SOC. First, then, let us take three of the four and, as we see that two of these are split up and scattered each one into many, let us try, by collecting each of them again into one, to learn how each of them was both one and many.

PRO. If you could tell me more clearly about them, I might be able to follow you.

And it’s supposed to lack humor!

Socrates and Protarchus are debating whether the highest good is pleasure or knowledge.  They have already agreed at this point that the life that mixes both is preferable to one consisting of either on its own (pleasure without knowledge or knowledge without pleasure).  They are now trying to determine which of the two gets “the second prize” and so enter into a long and interesting discussion on the nature of pleasure and of knowledge.  In the course of this discussion, they touch on issues of perception, memory and false opinion (as in the Theaetetus), as well as on the notion of analogy between the human being and the cosmos, each composed of the four elements and guided by a Soul (as in the Timaeus).

But for me by far the most interesting part of the dialogue was a long exploration of mixed pleasure and pain.  First Socrates addresses those sensations that affect both body and soul.  This part of the dialogue uses language drawn from the medical writers, but a really interesting article* shows how an undercurrent of the passage evokes the poetic discourse of erotic love.  When Socrates describes the response of someone moving from pain to pleasure, then, we have been prepared to think specifically of sexual pleasure (e.g. 47a).  As a sort of code for this Socrates talks about “itching” and “scratching.”   Of course these are precisely the terms he used in the Gorgias to talk about the life of a kinaidos; do you suppose then that psora, or itching, has this connotation more broadly?  I’m dying to investigate.  (The Loeb edition, by the way, is hopeless on this sort of thing.)

But even more intriguing is the passage that follows, concerning pleasures that affect the soul only.  Here (unlike in the earlier discussion) he does mention eros, along with other emotions such as anger, fear, yearning, mourning, jealousy and envy.  Interestingly (and I’m pretty sure in opposition to Aristotle’s account of many of these emotions) he identifies all of these as producing a mix of pleasure and pain.  This seems to me really psychologically astute.  But it’s more intuitively obvious in the case of some emotions than others.  In the case of anger (which even Aristotle admits is a pleasurable as well as a painful feeling) he quotes Homer’s excellent line calling anger “sweeter than honey that drips from the comb” (47e, quoting Iliad xviii 110).  But in the case of mourning, he adduces tragic pleasure as his proof: “you remember, too, how people enjoy weeping at tragedies?” (48a).  Lots of philosophers see this phenomenon as a paradox (i.e. that painful emotions such as pity and fear can generate pleasure in the context of art), but Socrates here simply extends tragic response to life in general; if we “enjoy weeping” (hama khairontes klaosi) at tragedies, then “not merely on the stage, but in all the tragedy and comedy of life, pain is mixed with pleasure” (50b).
I’m not going to argue with Socrates here, because I too sense that there is a pleasure of some sort to these negative emotions.  But what really interests me is that the passage contains what amounts to a theory of comedy, and although I’ve done quite a bit of reading around about comic theory I don’t think I’ve ever seen this passage cited.

After getting Protarchus to agree that there is pleasure in weeping at tragedies, Socrates asks him if this isn’t also the case at comedies, that “there also we have a mixture of pain and pleasure.”  I think this is to head off the possibility that there may be some unmixed pleasure of the soul apart from the contemplation of geometry (!) which is what will later be posited as such.  Protarchus, conveniently, isn’t so sure about comedy (“I do not quite understand” – thank you, Protarchus!), so Socrates develops at some length a notion of to geloion, or “the ridiculous” (although a better translation might be “the laughable”).  He defines the ridiculous as instances of ignorance (either of one’s material possessions, one’s physical attributes, or one’s virtues) in the weak – it is laughable, then, when someone harmless thinks they are richer or better-looking or wiser than they really are.  (Such ignorance in the powerful is excluded: in that case it is an evil and dangerous thing.)  But since ignorance is a misfortune, when we laugh we are laughing at misfortune, and laughing at misfortune is envy, and envy is painful… qed, laughing at comedy mixes pleasure and pain.

I don’t buy this; my sense of laughter at the alazon is pretty much entirely separate from anything I would acknowledge as envy (which I also consider more as pain at another’s good fortune rather than pleasure at another’s ill-fortune).  But the whole construct is intriguingly close to what Leon Golden has posited as Aristotle’s theory of comedy, based purely on the Poetics (with some supplements from the Rhetoric): that the emotion peculiar to comedy would have to be the opposite of pity, which Aristotle defines as nemesan, or pain at undeserved good fortune (contrasting pity, or pain at undeserved bad fortune).

It all really makes me think that laughter, for the Greeks, was a good deal more sinister than I believe it usually is for us!

*Anastasia-Erasmia Peponi, “Mixed Pleasures, Blended Discourses: Poetry, Medicine and the Body in Plato’s ‘Philebus'” CA 21.1 (2002) 135-160.  If you have access to JSTOR, you can find it here.