Logic
The shortest description nobody can certify
A string's complexity is the length of the shortest program that prints it. Counting shows almost every string has no short program, and diagonal arguments show nothing can compute the length, or even prove it large for any single string past a fixed point. All 16,777,216 three-state Turing machines leave only 95 strings on their tapes, and a compressor treats π exactly as it treats random bits.