At the core, each person is unknowable.

We'll never penetrate the secrets of the living, let alone the dead. I've spent my whole life trying to understand people, and all I've learned is that the deeper we look, the greater the mystery. At the core, each person is unknowable. Maybe that's the soul? I have to respect that. The mystery, in fact, is what I've loved the most, in people and in stories as well.”
― Sandra Scofield, Plain Seeing