Hm.... this opening paragraph should not contain the word "logic" inside its own definition.
Logic (from the Ancient Greek: λογική, romanized: logikḗ[1]), originally meaning "the word" or "what is spoken", but coming to mean "thought" or "reason", is generally held to consist of the systematic study of the form of valid inference. A valid inference is one where there is a specific relation of logical support between the assumptions of the inference and its conclusion. (In ordinary discourse, inferences may be signified by words like therefore, hence, ergo and so on.)