# Challenge B Intermediate Logic Unit 2 Foreman

## 7 terms

### formal proof of validity

a step by step deduction of a conclusion from a set of premises, each step being justified by an appropriate basic rule

### rule of inference

a valid argument form which can be used to justify steps in a proof

### rules of replacement

forms of equivalent statements

### conditional proof

a special rule in a formal proof which allows us to assume the andecedent of a conditional and, once we deduce the consequent, to conclude the the entire conditional

### reductio ad absurdum

a special rule which allows us to assume the negation of a proposition, deduce a self contradiction, then conclude the proposition

### truth-functionally complete

A set of logical operators is truth-functionally complete if and only if all possible combinations of true and false for two variables are derivable using only those logical operators

### The logical operator NOR (∇)

is equivalent to ~(p∨q), and truth-functionally complete