logic - n.
1 a the science of reasoning, proof, thinking, or inference. b a particular scheme of or treatise on this.
2 a a chain of reasoning (I don't follow your logic). b the correct or incorrect use of reasoning (your logic is flawed). c ability in reasoning (argues with great learning and logic). d arguments (is not governed by logic).
3 a the inexorable force or compulsion of a thing (the logic of events). b the necessary consequence of (an argument, decision, etc.).
4 a a system or set of principles underlying the arrangements of elements in a computer or electronic device so as to perform a specified task. b logical operations collectively.

logician n. [ME f. OF logique f. LL logica f. Gk logike (tekhne) (art) of reason: see LOGOS]