Tjyylli

Where is the fallacy here:

1. whatever is natural is not unnatural




2. whatever is unnatural is not natural




3. the phenomenon of cats being born into this world is natural




4. the phenomenon of rabbits being born into this world is not the phenomenon in point 3

Conclusion: the phenomenon of rabbits being born into this world is unnatural

It appears that you are treating "is" as an equality operator. There are contexts where "is" denotes equality ("one plus one is two"), but in other cases where it denotes something else, such as subset ("cats are mammals") or attribute ("cats are furry"). If we replace "cats being born in the world" with "A", "natural" with "B", and "rabbits being born in the world" with "B", then your argument is "A is B, C is not A, therefore C is not B." If "is" is denoting equality, then this would be a valid argument. But the first and last "is" are denoting attribute. The argument "Cats are furry, dogs are not cats, therefore dogs are not furry" would be a shorter version of this fallacy. Or "five is prime, seven is not five, therefore seven is not prime".

This can be seen as an equivocation fallacy (using "is" in different sense), denying the antecedent (we have the true statement "if C were A, then C would be B", and you're denying the antecedent "C is A" to negate the conclusion), false dichotomy (the argument boils down to claiming that everything is either A or not B).

Here is the argument:

1. No N is not-N.




2. No not-N is N.




3. All C are N.




4. No R are C.

Thus: No R are N.

The syllogism is invalid for two reasons. First, the third premise denies the antecedent (cats) of the fourth. There can be other animals that are normal. Wikipedia: Denying the antecedent; Formal fallacy.

Second, a term that is distributed in the conclusion (normal) is not distributed in the major premise (all cats are normal). Wikipedia: Illicit major.

The first two premises are not needed except as definitions. The second two, about cats and rabbits, state actual relationships between categories,

The argument is basically the fallacy of Denying the Antecedant. ~C, C → N |- ~N

• RabbitBirths are not CatBirths,


• CatBirths are NaturalPhenomena,


• therefore RabbitBirths are not NaturalPhenomena.

R → ~C , C → N |- R → ~N

Your error here is defining "normal" as a single set of things to which something either belongs or doesn't. That's not a useful (or normal) definition. Things are only normal or abnormal in context, compared to others of their kind. Are they a common or typical example of that kind, or are they an unusual or rare example? Normal cats have long tails (Manx cats might be considered abnormal). But a cat would be, say, a very abnormal voter, or an abnormal vehicle (more typical voters being human and more typical vehicles being machines). A perfectly normal person, likewise, would be an abnormal meal (cannibalism being rare), and a perfectly ordinary vehicle (say a bicycle) would be an unusual piece of art to hang on a wall.

You then make a second error in assuming that the statement "cats are normal" is equating the set of cats with the set of normal things. That's not what "are" means in this context. A more appropriate reading of that sentence would be to make cats a subset of normal things.

You imply in point 3 that all cats are normal. I don't know the specific name of the fallacy, but your argument is invalid because you didn't state that all things normal are cats, only that all cats are normal.