This Or That Fallacy

The fallacy is this. The people who argue this take a true statement: you must choose X or Y [In this case callbacks vs virtual functions ( which as far as I know, are the only two options )] and pervert it into: you must chose Z vs Y where Z is one variant of X. [ In this case message maps vs virtual functions ].

You then prove that Y is not a good option and claim Z, ignore the whole range of options that are not Z. In this case justifying the bastardisation of a callback system by heavily abusing macros because virtual functions don't work.


The fallacy is that you must choose between A and B - the belief that there are no other options.

(Actually, you must always choose between the options you know about, ignoring all the possible options that you don't know about. ;-)

Uhm. No. Your approach to problem solving suggests only using known methods, and never inventing new ones. That is not a good approach. -- Thaddeus Olczyk

It's is sometimes called the Excluded Middle; I think it goes back to Mr Aristotle. It is related to the Slippery Slope, which says, roughly, if we give them an inch they'll take a yard. That presents the choice as "nothing" or "a yard" and the middle choice of "an inch" is excluded. -- David Saff

I use this fallacy with my daughter when I want her to get dressed: "do you want to wear this outfit or that outfit?". I've also heard this called a Grandma Question. -- Phil Goodwin

As any mathematician knows, the answer to such a question should be yes -- Stephan Houben

But the whole point of this page is that sometimes the correct answer to the question is no. -- A mathematician

I think the answer is mu. See Mu Answer.


A fallacy that Microsoft seems to commit often (see Mfc Message Map Fallacy).

I've taken the liberty of splitting the MFC message map vs virtual function argument off into Mfc Message Map Fallacy. I'm not sure how to tidy up the rest of this page, but I've done my best. If anyone would prefer me to replace the original, let me know. --Roger Lipscombe


Grandma Question is a variant, and Slippery Slope is related to this fallacy.

See original on c2.com