pashut peshat

Talmudic, yeshivish, or Jewish way of slapping you in the face with what you thought was a novel idea but is actually just the simple obvious explanation.

It's also a way of saying something is simple, literal and obvious. It literally translates to, the simple, simple interpretation.

Often used by teachers against their students, or learning partners / chavrutas.

It's pashut peshat that one is different than two.

Or

Person 1: makes some obvious observation or statement
Person 2: it's pashut peshat!