Originally Posted by

**Cheerful Charlie**

No elephant is a squid.

Joe is an elephant.

Joe then cannot be a squid.

Therefore, Joe is a squid

Any sort of "logic" that can conclude Joe is a squid is obviouslt flawed.

Let me try to persuade you otherwise.

Argument 3:

P1: No giraffe is an elephant.

P2: Joe is either a squid or a giraffe.

P3: Joe is an elephant.

C: Therefore, Joe is a squid.

Is that valid?

Consider, for example, the following argument:

Argument 4:

P1: No giraffe is a mollusc.

P2: Joe is either a squid or a giraffe.

P3: Joe is an mollusc.

C: Therefore, Joe is a squid.

If you take a look, you will see that Argument 4 and Argument 3 have

**exactly the same form**. Before I go on, I would like to ask you whether you think Argument 3 and Argument 4 are both valid, or neither, or only one (depending on the answer, I might or might not try to convince you that the original OP argument is valid).