Understanding the logic behind proof by contradiction.
88188
Explain proof by contradiction.
109685
An invalid argument, the conclusion of which is a tautology
12186
How does predicate logic handle contradictory statements about something that does not exist?
32441
How to prove or disprove statements about sets
143627
Use the Fitch system to prove the tautology (p ∨ ¬p)
143248
What approach should I take to establish this logical proof?
29629
Distinguishing between valid and fallacious arguments (propositional calculus)
22584
Can we prove that a statement cannot be proved?
42590
Understanding implication in logic truth tables (excerpt from textbook)
72185
The negation of a limit condition, Spivak style.
127733
How to prove De Morgan’s laws without using contradictions
109858
How could a statement be true without proof?
31299
Using the Fitch system, how do I prove $((p \implies q) \implies p)\implies p$?
129185
Understanding the truth value for ⇏ when antecedent is false and consequent is true.
87928
Proof of logical equivalence of biconditional and other proposition
17073
Using proof by contradiction vs proof of the contrapositive
136577
In formal logic, how is it possible for an argument with a contradictory conclusion to be valid?