Logic

Logic (Greek λογίζω I reckon, I count, from λόγος a word) is a branch of philosophy that deals with and attempts to guide the faculty of human reason.

Logic was invented by Greek philosopher Aristotle. No other civilization can lay claim to its invention. The rules of logic were codified by Aristotle several centuries before the coming of Christ, and were used by St. Paul in his theological discussions. Logic was very appealing to Jewish scholars, and many instances of logical reasoning appear in the Old Testament.

Logic helps discern truth, which helps lead a person to the saving grace of a relationship with God:

• Come, let us reason together.
• You shall know the truth, and the truth shall set you free.

The forms and methods of logic are codified as formal logic, a highly structured set of rules for deductive reasoning. Formal logic depends totally on mutual agreement between and among parties to any discussion on fundamental premises and other facts asserted as evidence. If the parties cannot agree on fact, then formal logic is unavailing. Some logical fallacies are formal-logical failures.

Symbolic logic is formal logic expressed in an abstract language, similar to the language of algebra. It uses variable names for propositions and various symbolic operators to stand for formal logical processes like conjunction (p and q), disjunction (p or q or both), and implication (p implies q or if p, then q). Symbolic logic does not differ from formal logic, except that in that the latter is written in the same language in which human beings regularly write and speak, whereas symbolic logic uses a language of its own.

COCKSUCKERS

Logic and common sense

Informal logic consists of "common sense" and other, rather loose rules that people employ while making most decisions and even in debate. It is unstructured, and depends largely on one's view of "the reasonable"--which in turn is that body of facts that one reasonably expects to exist. Informal logic also includes inductive reasoning. The thresholds of what is "reasonable" and what is not, are inexact and subject to change with the receipt of sufficient contrary evidence--and again, what constitutes "sufficiency" in this context might vary from person to person. Most logical fallacies are failures in informal logic.

See Also

• Aristotle, "Organon"
• Branden, Nathaniel, The Benefits and Hazards of the Philosophy of Ayn Rand
• Rand, Ayn, The Virtue of Selfishness and other collections of essays