Webster 1913 Edition



, F.
, L.
, Gr.
), fr.
belonging to speaking or reason, fr.
speech, reason,
to say, speak. See
The science or art of exact reasoning, or of pure and formal thought, or of the laws according to which the processes of pure thinking should be conducted; the science of the formation and application of general notions; the science of generalization, judgment, classification, reasoning, and systematic arrangement; the science of correct reasoning.
is the science of the laws of thought, as thought; that is, of the necessary conditions to which thought, considered in itself, is subject.
Sir W. Hamilton.
Logic is distinguished as pure and applied. “Pure logic is a science of the form, or of the formal laws, of thinking, and not of the matter. Applied logic teaches the application of the forms of thinking to those objects about which men do think.”
Abp. Thomson.
A treatise on logic;
as, Mill’s

Webster 1828 Edition



[L. id; Gr. from reason, to speak.]
The art of thinking and reasoning justly.
Logic is the art of using reason well in our inquiries after truth, and the communication of it to others.
Logic may be defined, the science or history of the human mind, as it traces the progress of our knowledge from our first conceptions through their different combinations, and the numerous deductions that result from comparing them with one another.
Correct reasoning implies correct thinking and legitimate inferences from premises, which are principles assumed or admitted to be just. Logic then includes the art of thinking, as well as the art of reasoning.
The purpose of logic is to direct the intellectual powers in the investigation of truth, and in the communication of it to others.

Definition 2024



See also: lògic and -logic


Alternative forms



  1. logical


logic (countable and uncountable, plural logics)

  1. (uncountable) A method of human thought that involves thinking in a linear, step-by-step manner about how a problem can be solved. Logic is the basis of many principles including the scientific method.
  2. (philosophy, logic) The study of the principles and criteria of valid inference and demonstration.
    • 2001, Mark Sainsbury, Logical Forms An Introduction to Philosophical Logic, Second Edition, Blackwell Publishing, p. 9
      An old tradition has it that there are two branches of logic: deductive logic and inductive logic. More recently, the differences between these disciplines have become so marked that most people nowadays use "logic" to mean deductive logic, reserving terms like "confirmation theory" for at least some of what used to be called inductive logic. I shall follow the more recent practice, and shall construe "philosophy of logic" as "philosophy of deductive logic".
  3. (uncountable, mathematics) The mathematical study of relationships between rigorously defined concepts and of proof of statements.
  4. (countable, mathematics) A formal or informal language together with a deductive system or a model-theoretic semantics.
  5. (uncountable) Any system of thought, whether rigorous and productive or not, especially one associated with a particular person.
    It's hard to work out his system of logic.
  6. (uncountable) The part of a system (usually electronic) that performs the boolean logic operations, short for logic gates or logic circuit.
    Fred is designing the logic for the new controller.


Related terms

Derived terms



logic (third-person singular simple present logics, present participle logicking, simple past and past participle logicked)

  1. (intransitive, pejorative) To engage in excessive or inappropriate application of logic.
    • 1884, Orestes Augustus Brownson, Controversy, page 21:
      Nay, is not the author himself "logicking" against logic, from the beginning of his book to the end ?
  2. (transitive) To apply logical reasoning to.
    • 2010, James Ellroy, Blood's a Rover, page 90:
      He logicked that one out. He snuck into Haiti and scored herbs to rev him and calm him.
  3. (transitive) To overcome by logical argument.
    • 2010, Jade Lee, Wicked Surrender:
      If things had gone as usual this night, if Kit had not logicked her into agreement, then she probably would have opened the door tonight.

External links

  • logic in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
  • logic in The Century Dictionary, The Century Co., New York, 1911
  • logic at OneLook Dictionary Search