Premises

Goals

1. Describe premises.
2. Skillfully used premises.

What?

A premise is a proposition that is assumed or asserted to be true and is used as a reason to support a conclusion in an argument.

Examples

Example 1: Categorical Syllogism

This example shows how two premises lead to a conclusion using a categorical structure.

1. Premise 1: All mammals are warm blooded.
   
2. Premise 2: Whales are mammals.
   
3. Conclusion: Therefore, whales are warm blooded.

Logic Structure: Categorical syllogism
Comment: This argument is valid and sound if the premises are true.

Example 2: Disjunctive Syllogism

This example uses a disjunction (either/or) and eliminates one possibility to reach the conclusion.

• Premise 1: Either the light is burned out or the power is out.
  
• Premise 2: The light is not burned out.
  
• Conclusion: Therefore, the power is out.

Logic Structure: Disjunctive syllogism
Comment: The structure is valid. Soundness depends on whether the premises reflect reality.

Example 3: Enthymeme (with Hidden Assumption)

This example includes a visible premise and a hidden assumption that is needed to reach the conclusion.

• Premise: Exercise is good for you.
  
• Conclusion: Thus, you should exercise.

Hidden Assumption: You should do things that are good for you.

Logic Structure: Enthymeme
Comment: The argument becomes stronger when the hidden assumption is stated and evaluated.

Rationale (Why?)

Here is why premises are worth learning about and becoming skilled with.

Premises are a fundamental part of CT (critical thinking).

CT depends on its essential parts to deliver its benefits—such as truth, wise actions, clarity, and sound reasoning.

Since premises are one of these fundamentals, they are worth understanding and using skillfully.

Skillful Premise Use (How To)

Step 1: Identify Premises in the Argument

• Break the argument into components: issue, conclusion, logic structure, premises, subconclusions, assumptions (implicit and explicit), definitions, etc.

Step 2: Evaluate Each Premise

Use the following checklist. An answer of “no” likely indicates a weakness:

1. Is the premise a proposition (i.e. truth-apt)?
2. Does the premise clearly support the conclusion or a sub-conclusion?
3. Is the premise relevant and necessary to the argument?

If the premise is objective:

• Has it been proven with logic or evidence?
• Is it publicly verifiable or cited?
• Is it testable or falsifiable?

If the premise is subjective:

• Has the arguer explained why others should accept it?
• Is it reasonable given the context, values, or goals?

Step 3: Consider the Argument as a Whole

• Integrate your evaluation of premises with:
  • The soundness of the logic
  • Clarity and relevance of definitions
  • Stated and unstated assumptions
  • Inclusion of opposing views and counterarguments

Analysis (Breakdown of Main Ideas)

Here are some of the key ideas used on this page.

Proposition

A statement that is either true or false.

Premise

A proposition offered as a reason to support a conclusion in an argument.

A good premise is relevant, truth-apt, and helps justify the conclusion.

Assert

To assert is to state or declare that something is true, typically with confidence.

Assertion is done by an arguer.

Assumption

A proposition accepted without proof or direct support, often taken for granted in an argument.

Assumptions may be explicit (clearly stated) or implicit (unstated but necessary for the reasoning to work).

True

A statement is true if and only if it accurately reflects reality—that is, the way things actually are.

Reason

A proposition offered as support for a conclusion; something that gives grounds to believe a statement is true or that an action is best.

Conclusion

The proposition that the other statements (the premises or reasons) are intended to support.

It represents what the arguer aims to justify or prove through the argument.

Argument

A set of propositions in which one (the conclusion) is claimed to follow from the others (the premises or reasons).

An argument has a conclusion and at least one premise.

Arguer

A person or group who presents an argument by stating a conclusion and offering reasons or premises to support it.

Subconclusion

A conclusion that also functions as a premise in support of a further conclusion.

Objective Statement

A proposition whose truth is evaluated based on evidence and logic; not on people’s opinions.

Subjective Statement

A proposition that reflects personal belief, preference, or experience; its truth may vary across individuals.