Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises due to the structure of arguments alone, independent of their topic and content. Informal logic is associated with informal fallacies, critical thinking, and argumentation theory. It examines arguments expressed in natural language while formal logic uses formal language. When used as a countable noun, the term "a logic" refers to a logical formal system that articulates a proof system. Logic plays a central role in many fields, such as philosophy, mathematics, computer science, and linguistics.
Young America's dilemma: Shall I be wise and great, or rich and powerful? (poster from 1901) This is an example of a false dilemma: an informal fallacy using a disjunctive premise that excludes viable alternatives.
Bertrand Russell made various contributions to mathematical logic.
Image: Aristotle Altemps Inv 8575
Image: Avicenne Avicenna Ibn Sina (980 1037) CIPB2067
Logical reasoning is a mental activity that aims to arrive at a conclusion in a rigorous way. It happens in the form of inferences or arguments by starting from a set of premises and reasoning to a conclusion supported by these premises. The premises and the conclusion are propositions, i.e. true or false claims about what is the case. Together, they form an argument. Logical reasoning is norm-governed in the sense that it aims to formulate correct arguments that any rational person would find convincing. The main discipline studying logical reasoning is logic.
Based on many individual observations of black ravens, inductive reasoning can be used to infer that all ravens are black.
Doctors use abductive reasoning when investigating the symptoms of a patient to determine their underlying cause.
Analogical reasoning can be used to transfer insights from animal experiments to humans, like in the case of research on obesity and hypertension performed on Zucker rats.