Formal logic
Formal logic is a logic that ignores the content of thought and studies only the conditions of validity in the form of reasoning. If you lie at first, you will have to lie differently to rationalize it, and you will have to lie in succession. If you lie or not, it will be common in the world. It is because the reasoning from the first premise is approved as valid. Formal logic questions the formal basis for the validity of this reasoning. It has no relation to the meaning of thought, that is, quality and inclusion, and is also called 'extensional logic' because it considers only the form, ie, Modern symbol logic is a new form logic that thoroughly quantifies and symbolizes thought.