Quiz 1 - Logic & Critical Thinking

Propositions

A declarative statement that makes an assertion about what is or isn't the case (has to be true or false not both) Ex: Grass is green OR Denver is in the state of Colorado Ex of a NON preposition: Close the door

Validity and soundness apply to only what?

ONLY ARGUMENTS

Truth and falsity apply to only what?

ONLY PROPOSITIONS

Assertoric

To claim something is or is not the case

Inference Indicators

Words that signal that particular statements may be functioning as a premise or as the conclusion.

Example of a valid argument

All A are B No B are C No A are C

Example of an invalid argument

All A's are F X is F X is an A

Soundness

An argument is sound if and only if it is valid and all the premises are TRUE

Validity

An argument is valid if and only if it is such that if the premises are all true, it is not possible for the conclusion to be false (the truth of its premises guarantees the truth of its conclusion--it is IMPOSSIBLE for the premises to be true and the conclusion to be false--an argument is valid if the truth of the premises logically guarantees the truth of the conclusion)

Arguments

A set of propositions in which one of the propositions is intended to offer evidence in support of some other proposition

What does it really mean if something is true or false?

It makes sense to think of

Truth values

Properties of propositions (which can be true or false) that are binary and correspond to reality.

Conclusions

Proposition, the truth of which is meant to be demonstrated by a premise (A proposition whose truth has been inferred on the basis of other propositions assembled with it in a logical argument.)

Premises

Propositions offered as evidence for a conclusion. It should be able to stand alone as a complete thought

Examples of premise indicators

Since, because, for, as, follows from, as shown by, as indicated by, for the reason that, may be inferred from, in view of the fact that

What arguments can be considered valid?

TT, FF or FT

Logic

The formal study of the methods and principles used to discriminate between good and bad reasoning

Inductive reasoning

The intent is to give good reasons to believe the conclusion is probably true

Deductive reasoning

The intent is to give reasons whose truth logically necessitates the truth of the conclusion (certainty)

Examples of conclusion indicators

Therefore, hence, so, accordingly, in consequence, consequently, proves that, as a result, for this reason, thus, it follows that, which shows that, infer that, we may infer