Definition

The study of correct reasoning and the principles that lead us to truth. Logic provides laws that cannot be violated if truth is to be maintained.

Definition

A self-evident assumption or belief accepted as true, though not provable. Example: Two parallel lines never meet.

Definition

Foundational beliefs or postulates that shape how we interpret reality. Example: An atheist presupposes “There is no God.”

Definition

A truth so obvious that it requires no proof. Example: I exist.

An argument that begins with axioms and leads to conclusions that must be true if the premises are true. Example:

• All men are mortal.

• Socrates is a man.

• Therefore, Socrates is mortal.
  
  

Reasoning from specific observations to general conclusions. The conclusion is probable, not certain. Example:

• All observed swans are white.

• Therefore, all swans are white. (until a black swan is seen).

Reasoning that infers the best explanation by showing alternatives lead to absurdity.

A thing is identical to itself. A = A.

Two contradictory propositions cannot both be true in the same sense at the same time.

Every proposition must be either true or false; there is no middle ground.

A flaw in reasoning.

• Formal Fallacy: Error in logical structure.

• Informal Fallacy: Error in content or faulty assumptions.

Using a word in two different senses to confuse an argument. Example: “evolution” (micro vs. macro).

One where the conclusion follows logically from the premises (though the premises may be false).

One that is both valid and has true premises, leading to a true conclusion.

The belief that truth and morality are relative to individuals or cultures, denying objective truth.