1. According to Irving Copi, logic is "the study of methods for evaluating the strength of arguments and reasoning."
2.Aristotle defined logic as "the science of the necessary laws and principles of thought and reasoning."
3.Bertrand Russell described logic as "the science of the necessary laws of thought, without which no real progress can be made in the understanding of the world."
4.Immanuel Kant defined logic as "the science of the rules of understanding and reason in general, and of the operations of the understanding and reason in particular."
5.Gottlob Frege characterized logic as "the science of the most general laws of truth."