Symbolism, Imagery, Allegory
Not the Stephen King novel, either. By "IT" we mean…well, what do we mean? That’s the question. Only it’s more like, what is Dean talking about with this IT business? Does he even know? And what is going on with this flagrant abuse of capital letters?
Dean tends to talk about IT when he’s talking about 1) time and 2) God. So IT has something to do with time and God. Also it’s capitalized, so that you don’t mistake IT for a pronoun when you’re reading. So it’s important; we get that. But what does it mean? IT becomes this thing that Dean seeks and then knows, insists that Sal knows, but won’t detail explicitly because he just doesn’t have the time. Musicians have IT, George Shearing definitely has IT, and because of IT, Dean is able to groove anywhere in America.
IT most likely is to Dean what this "pearl of wisdom" business is to Sal. It’s the end of the road. It’s what they’re searching for. But the problem with the Beat Generation was that they didn't know what they wanted. There’s a reason that IT is vague, and it’s because the desires of the Beat Generation were vague. That’s what makes their dissatisfaction so frustrating. Dean simply put a name on this thing that he doesn’t know he wants; he calls it IT.