The story goes that Pirithous, having heard of Theseus' prowess in battle, wanted proof of his courage and strength, and so, as all good heroes do, he went out to rustle some of Theseus' cattle in order to test him. A time honored tradition among demigods, and second only to stealing women-folk! Plutarch tells the rest of the story in his essay on Theseus:
[...]when the news was brought that Theseus pursued him in arms, he did not fly, but turned back and went to meet him. But as soon as they had viewed one another, each so admired the gracefulness and beauty, and was seized with such respect for the courage of the other, that they forgot all thoughts of fighting; and Pirithous, first stretching out his hand to Theseus, bade him be judge in this case himself, and promised to submit willingly to any penalty he should impose.
And that, as they say, was the beginning of a beautiful friendship. From that day forth, Theseus and Pirithous were like brothers, allies in everything and according to Ovid's Heroides, inseparable to the point of neglecting their other relationships, including their own sons (but then too, Phaedre isn't the most reliable of narrators, either, and bespelled by the gods in her lust for Theseus' son, besides).
|© Marie-Lan Nguyen / Wikimedia Commons
Which is Pirithous and which is Theseus
I couldn't tell you, honestly.
Personally, I think the bromance of Pirithous and Theseus belongs up there with Achilles and Patroclus, and it's a real shame they don't get more press in pop culture. That um, might account for their continued and repeated presence on my blog. If you were wondering.