Traditional Logic Reference Sheet

The science of correct reasoning

A word or group of words that can serve as the subject or predicate of a proposition

The set of all things to which the term applies

The extension of 'dog' is all dogs

The set of attributes that define the term

The intension of 'dog' includes 'animal', 'domesticated', etc.

A term that refers to all members of a class (e.g., 'all dogs')

A term that refers to some (but not all) members of a class (e.g., 'some dogs')

A statement that gives the essential meaning of a term by stating its genus and specific difference

A statement that is either true or false

A (All S are P), E (No S are P), I (Some S are P), O (Some S are not P)

A-proposition (universal affirmative)

E-proposition (universal negative)

I-proposition (particular affirmative)

The term about which something is affirmed or denied

The term that is affirmed or denied of the subject

The linking verb ('is' or 'are') that connects subject and predicate

Two propositions that cannot both be true and cannot both be false (A vs O, E vs I)

Two propositions that cannot both be true but can both be false (A vs E)

A deductive argument with two premises and a conclusion

Major term (predicate of conclusion), minor term (subject of conclusion), middle term (in both premises)

The premise containing the major term (predicate of the conclusion)

The premise containing the minor term (subject of the conclusion)

Man/men

The conclusion follows necessarily from the premises (regardless of whether premises are actually true)

It is both valid AND has true premises

4 (based on the position of the middle term)

An error in reasoning that makes an argument invalid

Attacking the person making the argument instead of the argument itself

Misrepresenting someone's argument to make it easier to attack

Assuming the truth of the conclusion in one of the premises

Introducing an irrelevant topic to divert attention from the original issue

Claiming something is true because an authority figure says so, even when they lack relevant expertise

Drawing a broad conclusion from too few examples

Presenting only two options when more exist

Claiming that one event will inevitably lead to a chain of negative consequences without justification

Using a word with two different meanings in the same argument to mislead

Reasoning from general principles to specific conclusions (if premises are true, conclusion must be true)

Reasoning from specific observations to general conclusions (conclusion is probable, not certain)

Validity is about the structure of an argument; truth is about whether statements correspond to reality

A condition that must be present for an event to occur (but may not be sufficient alone)

Water is necessary for life but not sufficient

A condition that, if present, guarantees the event will occur

Being a dog is sufficient for being an animal