Critical Reasoning - Week 4

When is a particular argument deductively valid?

A particular argument is deductively valid if and only if it is an instance of a valid form.

When is an argument form deductively valid?

An argument form is deductively valid if and only if there are no instances of that form in which all the premises are true and the conclusion is false.

What is a compound sentence?

A sentence is compound if and only if it logically contains another complete sentence as a component.

What is a simple sentence?

A sentence is simple if and only if it is not compound.

What is a sentential operator?

A sentential operator is an expression containing blanks such that, when the blanks are filled with complete sentences, the result is a complete sentence.

When is a sentential operator truth-functional?

A sentential operator is truth-functional if and only if the truth or falsity of a compound sentence containing that operator is completely determined by the truth or falsity of its component sentences.

What is a counterexample to an argument form?

A counterexample to an argument form is an instance of that form in which all the premises are true and the conclusion is false.

When is an argument form deductively valid (in terms of counterexamples)?

An argument form is deductively valid if and only if it has no counterexample.