PHIL 1230 Lesson 5 — Implicit Premises and Inductive Arguments

What is an implicit (unstated) premise?

An unexpressed assumption required to link the premises to the conclusion.

What is a bridge assumption?

An implicit premise that connects disparate ideas in an argument.

Smoking/Health implicit premise example: Premise: Smoking causes cancer. Conclusion: You should quit. What is the missing bridge?

Smoking is bad for your health and should be avoided.

What is inductive reasoning?

Reasoning where premises make the conclusion likely, but not guaranteed.

Lottery example of an inductively strong invalid argument:

Holding 500 of 1000 tickets makes winning likely, but not certain.

What is deductive intent?

The intention that the truth of premises guarantees the conclusion.

What is inductive intent?

The intention that the truth of premises makes the conclusion probable.

How does inductive strength differ from validity?

Inductive strength comes in degrees, while validity is all-or-nothing.

Are deductively valid arguments defeasible?

No, adding new premises cannot destroy deductive validity.

Are inductively strong arguments defeasible?

Yes, adding new premises can weaken or destroy inductive strength.

Can an inductively strong argument have false premises?

Yes, strength depends on structural support, not actual premise truth.

What is a cogent argument?

An inductively strong argument with all true premises.

What does validity measure?

Whether true premises strictly guarantee a true conclusion.

What does inductive strength measure?

Whether true premises make a conclusion probable.

What is a circular argument (begging the question)?

An argument that assumes its own conclusion in its premises.

Why is circularity a flaw in a good argument?

It fails to provide independent support for the conclusion.

What is a relevant premise?

A premise that logically bears on the truth of the conclusion.

What is a credible premise?

A premise that is believable and well-supported.

What makes a good argument beyond validity and strength?

Credible, relevant premises and avoiding circularity.

What is the main difference between deductive and inductive arguments?

Deductive aims at certainty; inductive aims at probability.

Can a deductively invalid argument be inductively strong?

Yes, most inductive arguments are deductively invalid.

How do you identify an unstated premise?

Look for logical gaps between the stated premises and the conclusion.

What makes an inductive argument weak?

Premises that provide little to no probabilistic support for the conclusion.

What is a sound argument?

A valid argument with all true premises.

What is a strong inductive argument?

An argument where true premises make the conclusion very likely.