When Jove saw that they had such audacity as to expose themselves to danger [kidnapping Helen], he bade them in a dream both go and ask Pluto on Pirithous’ part for Proserpine in marriage (Hyginus, Fabulae, 79).
|another shot of Ceres/Demeter|
Regardless, I have to wonder: would Pirithous have thought to abduct Persephone if it hadn't been for Zeus's influence and irritation with the pair of them? Granted, there aren't a lot of other daughters of Zeus for him to claim who aren't goddesses (according to Theoi, he only has two: Helen and Herophile of Libya), but might he have been more inclined to go on some less hazardous adventure elsewhere to find one?
Now, Hyginus also says that Heracles pulls them both back out of the underworld, but Apollodorus says otherwise in The Libraries:
And being come near to the gates of Hades he found Theseus and Pirithous, him who wooed Persephone in wedlock and was therefore bound fast. And when they beheld Hercules, they stretched out their hands as if they should be raised from the dead by his might. And Theseus, indeed, he took by the hand and raised up, but when he would have brought up Pirithous, the earth quaked and he let go.
Pirithous being Pirithous, I'm not sure it would surprise me all that much if he got it into his own head that Persephone wanted him, and it would be a good idea to go steal her, for which he would then deserve the punishment of being trapped in Hades for eternity. But if he only went after Persephone because of Zeus? Well, that changes things. Why shouldn't Pirithous follow the direction of the King of the Gods, with all hope of success in his venture? With Zeus' blessing, how could he fail?
It isn't all that different from Paris' motivations in stealing Helen, much later. Not that his excursion worked out any better, really. But it certainly changes things, either way. In this instance, even if Pirithous might have had the gall to go after Persephone on his own, would Theseus have had the audacity to go with him? Would he have leant his support to such a venture, pact or not? Would they have turned around and come home, halfway there?
Theseus might have returned before Helen's brothers arrived to steal her back, preserved his throne and his kingship, and Pirithous might have not spent the rest of eternity in the chair of forgetfulness. Perhaps they both would have gone on to Troy, forming a trio of cronies with Nestor, and lived or died there instead.
How many sins did the gods first impose upon their heroes, just for the excuse of punishing them? And was Pirithous a victim of his own Hubris, or the gods' desire to remind him just WHO exactly was boss? But one thing I don't wonder about when I read these stories is this: the gods matter to the outcomes, and neither the characters nor the stories themselves are the same when you strip them out.