Ladyhawke's moment of truth (see the discussion on Go, below) comes, I think, when Philippe says to the monk Imperius, "Every happy moment in my life has come from lying." It's a throwaway line (as moment-of-truth lines often are), but it highlights how important lies are to all of us.
Philippe carries on a running conversation with God about this very subject. He protests that God is confusing him and preventing him from learning moral lessons. But learn he does. By the end of the film he is putting himself in harm's way to help his friend Navarre without thinking, Navarre's rather serious threats notwithstanding.
He could have let the wolf drown. Nobody would have blamed him. And he would have been free of all obligations.
But he can't. Maybe it's all the talking with God. Maybe it's Isobeau's beauty. Maybe it's Navarre's great big sword. Maybe it's just because he is us and we couldn't bear watching ourselves fail to help out in such a situation.
Because, of course, that's exactly the purpose Philippe serves in this story -- he is us. Identification, anyone? We identify with Philippe, with his sarcastic recognition of the absurdity of not only his predictament but the entire world he inhabits. And that makes the whole story platable to an audience unused to the fantastic. If Philippe can accept it, we can shrug and say, "Okay, wolf, hawk, man, woman, got it."
But the problem with a character like Philippe is that he can't JUST comment on the fantastic nature of the story. He ends up questioning the very structure of the tale he finds himself caught up in: "I would like to think there's some higher meaning in this. It certainly would reflect well on you." When we hear that we of course laugh because it's such a presumptious thing for such a character to say, but also because we know perfectly that there IS a higher meaning in all this: the entire world created for this film exists solely to illustrate that "higher purpose" -- the story of Navarre and Isobeau.
Or is that it? Because you know, Navarre doesn't, like, learn much. Nor does Isobeau. They're more like a setting, a backdrop, really. A symbol of the division that exists in this world, that must be brought together and reunited before there can be peace and happiness. So maybe the "higher purpose" Philippe is hoping to see manifests within himself, as he finds the ability to make sacrifices on another's behalf. Not for any reward, and not because he's being forced to. Because the world isn't right and unless (to steal a few lines from Dr. Seuss) "UNLESS someone like you cares a whole awful lot, nothing is going to get any better. It's not."
I guess fundamentally, what's at the heart of Ladyhawke is the assertion that when you witness injustice and disruption, you become tasked with the responsibility to do something about it. Philippe doesn't get taught this lesson; God turns out to be a pretty bad instructor for our young hero. But he cannot turn away from the wrong he witnesses. He might insist that it's not his problem, a young man with prospects like his, but the truth of that statement cannot bring him happiness. Only the lie that he must help can do that.