Here's a few off the top of my head :)

- I'm studying logic and I'm not studying logic. Boom. [1]

- Since my logic has one more element than your logic, I'm studying second-order logic. [2]

- You're studying non-monotonic logic, but I could be wrong. [3]

[1] Principle of Explosion.

[2] Unbounded counting can't be expressed in first-order logics.

[3] http://plato.stanford.edu/entries/logic-nonmonotonic/