Formal Logic 1.2

Statements are sometimes called propositions.

In an argument the statement or statements that preceed the conclusion.

In an argument what follows the hypothesis.

• An argument that should be True based entirely on its internal structure or "intrinsicaly True."
• An argument whose conclusion should be related to or follow from the hypothesis.

• Rules that manipulate well-formed formulas (wffs) in a truth-preserving manner.
• Begin with the hypothesis (assumed True) and attempt to apply the manipulation rules in such a way as to end up with the conclusion (which must then also be True because truth is preserved under the rules).

A sequence of well-formed formulas (wffs) in which each wff is either a hypothesis or the result of applying one of the formal system's derivation rules to earlier wffs in the sequence.

Rules that state that certain pairs of well-formed formulas (wffs) A and B are equivalent.

Rules that say that if 1 or more well-formed formulas (wffs) that match the 1st part of the rule pattern are already part of the proof sequence, we can add to the proof sequence a new wff that matches the last part of the rule pattern.