Logic as a tool a guide to formal logical reasoning ( PDFDrive ) 305

Introduction rule Elimination rules ↔I [A] [B] ..

k

¬p → (¬q ∨ r) : T, q → ¬r : T, q → p : F

q : T, p : F

q :F

r :F

¬p : F

p :T

×

¬q ∨ r : T

¬q : T

q :F

×

r :T

×

The rule is sound, hence the argument is correct

Section 2.4 2.4.2

Introduction rule Elimination rules

(↔I)

[A] [B]

.

B, A↔B A

2.4.3 (c)

[¬p]1 [¬¬p]2 ¬p

⊥

p 1

¬¬p → p 2