Gödel's Incompleteness Theorem
A mathematical theorem stating that any finite axiomatic system rich enough for arithmetic will contain true statements that cannot be proven within that system, implying that any conceptual scheme can only scratch the surface of reality.
Videos Mentioning Gödel's Incompleteness Theorem

The Case Against Reality — Professor Donald Hoffman
Tim Ferriss
A mathematical theorem stating that any finite axiomatic system rich enough for arithmetic will contain true statements that cannot be proven within that system, implying that any conceptual scheme can only scratch the surface of reality.

Scott Aaronson: Computational Complexity and Consciousness | Lex Fridman Podcast #130
Lex Fridman
A mathematical theorem stating that in any consistent formal system containing basic arithmetic, there are true statements that cannot be proven within the system. Penrose uses this as part of his argument for uncomputable aspects of consciousness, an argument Aaronson finds unsound.