# What is the term the reasoning that inverse obejcts have inverse properties?

I recently came across the fallous reasoning that "if a is the opposite of b, then a must have all the opposite properties of b"
That is:

My dog is the opposite of my cat, and my cat has fur and is black, so my dog must have no fur and be white

What is the term for this?

• The problem here is not with the reasoning but with the premise, "my dog is the opposite of my cat" makes no sense on the usual understanding of "opposite". In fact, "my cat has fur and is black, and my dog has no fur and is white" could be offered as one way of explaining what the "opposite" as (ab)used here might mean. This could be a case of equivocation but in it the two occurrences of the same word are usually supposed to make sense independently, or rather two different senses. Dec 1 '16 at 1:22
• @Conifold That's just a simplified example I came up with. But of course, no two (real) objects or even concepts can be exact opposites of each other, so I suppose the overall reasoning is still fallous. Dec 1 '16 at 1:24
• @cat40:"if a is the opposite of b, then a must have all the opposite properties of b": Can we imagine anything (a thing or an idea) in this category? If 'yes', 'a' and 'b' are imaginable. Then this won't seem to satisfy your condition. I believe we can't even imagine such thing. What we call 'opposite' is opposite up to certain level only. Dec 11 '16 at 7:13
• (I don't know whether) That opposite word needs to kill all the properties of 'a' without leaving out anything. I think Philosophy can nothing to do with this matter. If so, a 'true-nullifier' might incarnate in english.stackexchange.com. So, for an apt word, IMHO, you'd better migrate to that site. Dec 14 '16 at 13:51