In everyday speech, we say, ‘You make a valid argument’, ‘You have a valid point’, ‘That’s a sound point’, ‘That’s a good argument’, ‘That’s a strong argument’ and so on. This is rather loose-speak.

Affirming the consequent is a logical fallacy whereby the arguer incorrectly concludes the cause (antecedent) because of the effect (consequent).

The branch of Philosophy concerning the nature of knowledge is Epistemology. Philosophers commonly identify three types of knowledge:

Modus tollens (Latin for ‘mode that denies’) is a valid form of logical deduction. It is a conditional form (if-then).

An ad hominem fallacy (Latin for ‘to the person’) is considered to be a logical error where someone attacks the personal traits or motives of the person making an argument, instead of addressing the actual substance or validity of the argument itself.

Modus ponens (Latin for ‘mode that affirms’) is a valid form of logical deduction. It is a conditional form (if-then) that we use frequently in everyday reasoning.

An argument from ignorance is NOT an argument from someone who is ignorant! Rather, it is a logical fallacy claiming something is true because it has not been proven false, or false because it has not been proven true. Thus, it uses a lack of evidence as evidence itself; this shifts the burden of proof.