2-3 Deductive Reasoning

2-3 Deductive Reasoning

A mechanic uses deductivereasoning to determine whatis wrong with your car.

2-3 Deductive Reasoning

A doctor will use deductive reasoning to diagnose apatient.

2-3 Deductive Reasoning

A lawyer uses deductive reasoningto build a case.

2-3 Deductive Reasoning

A construction foreman usesdeductive reasoning to determinewhat materials are needed ata work site.

2-3 Deductive Reasoning

And of course adetective uses deductive reasoning to solve crimes.

Deductive Reasoning

The process of reasoning logically from a givenStatement to a conclusion. AKA logical reasoning.

Deductive Reasoning

There are two laws used in logical reasoning:

LAW OF DETACHMENT

LAW OF SYLLOGISM

Deductive ReasoningLAW OF DETACHMENT

This law states that if a conditional statement is true, andIts hypothesis is true, then its conclusion is true.

Example: If it is raining outside, then I will use my umbrella.

It is raining outsideWhat can you conclude?

I will use my umbrella.

If p q is a true statement and p is true,Then q is true.

Deductive Reasoning

LAW OF DETACHMENT

More examples:

If Taylor and Nick make the softball teamThen they will get new hats.

Nick and Taylor made theSoftball team.

What can we conclude?

Taylor and Nick get a new hat.

Deductive Reasoning

LAW OF SYLLOGISM

This law of deductive reasoning allows you to make aConclusion if the following are true:

The conclusion of one true conditional statement is theSame as the hypothesis of another true statement.

Deductive Reasoning

LAW OF SYLLOGISM

If Tony goes to the movies, then he will eat popcorn.

If Tony eats popcorn, he will get indigestion.

Conclusion: If Tony goes to the movies, then he will getIndigestion.

If p q and q r are true statements, then p r is a true statement

Deductive Reasoning

LAW OF SYLLOGISM

Example: If it rains outside, the walkway will get wet.

If the walkway is wet, the walkway will be slippery.

What can we conclude from the Law of Syllogism?

If it is raining, the walkway will be slippery.

Can you use Law of detachment?

If a person lives in Omaha, then, he or she lives in Nebraska.

Tamika lives in Omaha

Yes, we could use detachment to determine the conclusion

Tamika lives in Nebraska.