Logic is derived from ‘Logos’ which meaning ‘Thinking’.
It is a systematic analysis of out thinking methodology & its product "thought".
A unit of thought is judgement.
When judgement is express in a language it becomes a sentence.
All sentences are converted into a logical structure.
Only in these structures the linguistic expressions are considered to be true, false or doubtful.
Logic is treated as a normative & not as a positive science.
In positive science the subject matter as studied 'as they are’.
Logic, ethics & aesthetics are the normative sciences, whose subject matter are studied from the ‘ought to be’ point of view.
Logic insists on how one ought to think rather than how one is actually thinking.