<P> There is no universal agreement as to the exact scope and subject matter of logic (see § Rival conceptions, below), but it has traditionally included the classification of arguments, the systematic exposition of the' logical form' common to all valid arguments, the study of inference, including fallacies, and the study of semantics, including paradoxes . Historically, logic has been studied in philosophy (since ancient times) and mathematics (since the mid-19th century), and recently logic has been studied in computer science, linguistics, psychology, and other fields . </P> <Table> <Tr> <Td> "</Td> <Td> Upon this first, and in one sense this sole, rule of reason, that in order to learn you must desire to learn, and in so desiring not be satisfied with what you already incline to think, there follows one corollary which itself deserves to be inscribed upon every wall of the city of philosophy: Do not block the way of inquiry . </Td> <Td>" </Td> </Tr> <Tr> <Td_colspan="3">--Charles Sanders Peirce, "First Rule of Logic" </Td> </Tr> </Table> <Tr> <Td> "</Td> <Td> Upon this first, and in one sense this sole, rule of reason, that in order to learn you must desire to learn, and in so desiring not be satisfied with what you already incline to think, there follows one corollary which itself deserves to be inscribed upon every wall of the city of philosophy: Do not block the way of inquiry . </Td> <Td>" </Td> </Tr> <Tr> <Td_colspan="3">--Charles Sanders Peirce, "First Rule of Logic" </Td> </Tr>

The following is not classic principle of logic