Valid or Invalid Syllogisms

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

All dentists are doctors.

Some dentists are women.

Therefore, some women are doctors.

• Valid

• Invalid

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

Many patriots are American.

All heroes are patriots.

Therefore, all heroes are American.

• Valid

• Invalid

Answer explanation

It doesn't say all patriots are American.

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

All birds are animals.

No cats are birds.

Therefore, no cats are animals.

• Valid

• Invalid

Answer explanation

It doesn't say all animals are birds.

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

No rationalists are empiricists.

Some rationalists are Europeans.

Therefore, some Europeans are not empiricists.

• Valid

• Invalid

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

All pigeons are birds.

All pigeons are winged animals.

Therefore, all winged animals are birds.

• Valid

• Invalid

Answer explanation

(It doesn’t say all winged animals are pigeons)

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

All ISIS members are terrorists.

Some ISIS members are not based in the Middle East.

Therefore, some based in the Middle East are not terrorists.

• Valid

• Invalid

Answer explanation

True, but invalid. The conclusion doesn't follow from the premises.

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

Mammals have lungs.

Fish are mammals.

Therefore, fish have lungs.

• Valid

• Invalid

Answer explanation

Untrue, but valid.

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

All Italians eat spaghetti.

Giovanni Rossi eats spaghetti.

Therefore Giovanni Rossi is Italian.

• Valid

• Invalid

Answer explanation

It doesn't say only Italians eat spaghetti. Rossi may well be Italian, but the argument is invalid.

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

Some monks are Tibetans.

All Tibetans meditate.

Therefore some monks meditate.

• Valid

• Invalid

Is this syllogism valid or invalid? Remember: it doesn't have to be true to be valid. Valid means that the conclusion necessarily follows from the premises:

All Alphas are Betas.

No Gammas are Betas.

Therefore no Gammas are Alphas.

• Valid

• Invalid