There's this girl in one of my classes. We went to high school together but I'm so shy I never asked her out. She's pretty with a lovely smile and a great personality. She's has a somewhat perverted sense of humor. She likes gaming and programming. Amazingly she has no boyfriend! She sent me and several other classmates her e-mail so I did what anyone would do: I Googled her e-mail address. I find out that she's a Redditor. She posts there several times a day.
First of all, Plato was a mathematician. He knew that numbers are just an abstract idea, not something you can pick up or eat. If you grab three objects, you're not actually holding the number three. You've just assembled a crude representation of it in the real world. It's not even exactly three, because there are slight variations in every physical object, making it humanly impossible to get exactly three of the same thing.
Plato decided that everything else in the material world works the same way. There's a perfect unchanging idea of "Horse" that we can only experience with our minds, whereas the animals we can actually see and touch are just imperfect imitations of Horse. They're always too young or too old, too fast or too slow, to be exactly like the one true Horse. Templates like this that exist only as ideas, and never in the real world, are called Platonic ideals.
Now apply this to Dirk. There's like fifty of him and he considers each to be as valid an existence as the others. This basically goes completely over Jake's head and he steps on a rake by asking "which is the real Dirk?" Another hero of Heart might answer this with "yes," but a Prince is inclined to narrow down the possibilities by destroying a couple. Even so, his whole personality is "inscrutable" in that nobody can just talk to the Platonic ideal of Dirk. (Or can they?)