**Do the premises support the conclusion?**

All dogs have four legs.

A dog is a mammal.

Therefore, a human has four legs.

**II) DEGREE OF CERTAINTY**

**DEDUCTIVE**

**Absolute certainty**

Validity/soundness

New premises do not affect

the validity of the argument and the

certainty of the conclusion

**INDUCTIVE**

probability, likelihood

strength

New premises could affect the strength of the argument and the probability of the conclusion.

**VALIDITY**

An argument is

**VALID**if__the truth of all of its premises force the truth of the conclusion__. If the premises are true, the conclusion must be true.**True premises & true conclusion**

All animals that suckle their young are mammals.

Whales suckle their young.

Whales are mammals.

Validity doesn’t guarantee the truth of either the premises or the conclusion. There are passages with true premises and true conclusions that are not valid.

All maple trees lose their leaves in the winter.

Pine trees do not lose their leaves in the winter.

All fish live in water.

It is possible to have

**a valid argument with false premises:**
True premises and true conclusion

True premises and false conclusion

False premises and true conclusion

False premises and false conclusion

**False premises, false conclusion False premises, true conclusion**

All insects have three eyes. All fish are mammals.

A cockroach is an insect. All whales are fishes.

Therefore, cockroach has three eyes. All whales are mammals.

Validity guarantees that if the premises are true, then the conclusion must be true.

An argument is deductively

**invalid**if it is possible for the**conclusion**to be false even though the**premises**are true.**True premises, false conclusion**

Sacramento is the capital of California.

Mike is fourteen feet tall.

**SOUNDNESS**

An argument is

**sound**if it is**valid**and its**premises**are true.
Greg is taller than Joe.

Joe is taller than Mike.

Therefore, Greg is taller than Mike.

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