...wait you don't know about it either?

[That is oddly confusing. But he'll explain anyway.]

There were rumors, as kids, that if you played the Master Persona Incarnation, you'd be able to see into the future. I played it with a few friends as a kid. There was a incantation too..."Master Persona, Master Persona, Please come to us!"

We blanked out and met Philemon and...that's how we ended up being able to use Personas.