Oh, you've been looking at the wrong type of philosophy, then.

[He thinks for a moment and then smiles. Let's continue on a theme. There's a strong possibility that Sherlock may know it, but it's a harder question all the same.]

Achilles challenges a tortoise to a race. So confident is he that he will win, he even offers to give the tortoise a head start. The tortoise however, through discourse, proves to Achilles that he himself would win the race and Achilles would forever be behind him. How did the tortoise so flummox the light of foot Achilles?