11.1 C ae

All animals are living things. At least one cabbage is a living thing. So at least one cabbage is an animal.

Invalid

All birds are animals. No tree is a bird. Therefore no tree is an animal.

Invalid

All murderers are criminals. Therefore, all non murderers are non-criminals.

Invalid

Alvin likes Jane. Jane likes Chris. So, Alvin likes Chris.

Invalid

If Lincoln was killed in an automobile accident, then Lincoln is dead. Lincoln is dead. So, Lincoln was killed in an automobile accident.

Invalid

It is possible that McGraw will win the next presidential election. It is possible that Lambert will win the next presidential election. Thus, it is possible that both McGraw and Lambert will win the next presidential election.

Invalid

f Lincoln was killed in an automobile accident, then Lincoln is dead. Lincoln was not killed in an automobile accident. Therefore, Lincoln is not dead.

Invalid

All physicians are singers. Madonna is a physician. Therefore, Madonna is a singer.

Valid

David is shorter than Saul. Saul is shorter than Goliath. It follows that David is shorter than Goliath.

Valid

Either 2 plus 2 equals 22 or Santa Claus is real. But 2 plus 2 does not equal 22. Therefore, Santa Claus is real.

Valid

Either we use nuclear power or we reduce our consumption of energy. If we use nuclear power, then we place our lives at great risk. If we reduce our consumption of energy, then we place ourselves under extensive governmental control. So, either we place our lives at great risk or we place ourselves under extensive governmental control.

Valid

If Lincoln was killed in an automobile accident, then Lincoln is dead. Lincoln is not dead. Hence, Lincoln was not killed in an automobile accident.

Valid

If Lincoln was killed in an automobile accident, then Lincoln is dead. Lincoln was killed in an automobile accident. Hence Lincoln is dead.

Valid

Samuel Morse invented the telegraph. Alexander Graham Bell did not invent the telegraph. Consequently, Morse is not identical with Bell.

Valid

Some humans are comatose. But no comatose being is rational. So, not every human is rational.

Valid