Deductive Reasoning Practice

All mammals are warm-blooded animals.

A dog is a mammal.

Therefore, a dog is a warm-blooded animal.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

No fish can fly.

A salmon is a fish.

Therefore, a salmon cannot fly.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

Some students are good at math.

John is a student.

Therefore, John is good at math.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

All cats are good swimmers.

My pet dog is a cat.

Therefore, my pet dog is a good swimmer.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

All roses are flowers.

Some beautiful plants are flowers.

Therefore, some beautiful plants are roses.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

If it rains, the ground gets wet.

It is raining.

Therefore, the ground is getting wet.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

Many people like chocolate.

Sarah is a person.

Therefore, Sarah likes chocolate.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

All triangles have four sides.

This shape is a triangle.

Therefore, this shape has four sides.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

Some doctors are rich.

Some rich people are happy.

Therefore, some doctors are happy.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false

All professional athletes train hard.

Michael Jordan was a professional athlete.

Therefore, Michael Jordan trained hard.

• Valid (logical): IF the premises are true, the conclusion MUST be true

• Sound: Valid AND the premises are actually true

• Invalid (illogical): Possible for the premises to be true and conclusion false