Explicio via absurdum

There is a logical fallacy called reductio ad absurdum, meaning attempting to establish a claim by showing that the opposite scenario would lead to absurdity or contradiction.

Sometimes I find that the opposite of reductio ad absurdum is actually helpful - using an utterly absurd or extreme example to explain a concept.

With my complete lack of Latin knowledge, I've been calling this "explicio via absurdum", but I welcome any corrections to my Latin!
 

This is particularly useful when trying explain something mathematical by a solely verbal medium, where you can't put numbers in front of your interlocutor's eyes and doing the math with plausible numbers would get you bogged down in arithmetic.

 

It's also useful when you don't know how the real numbers work, but you're trying to make the point that there's a range in which the numbers would work.

 

 

For example, I recently saw a discussion where some people seemed to think that interest rates were the major barrier to housing affordability, and didn't seem to recognize that housing prices themselves could be a barrier regardless of interest rates.

 

So here's how I would explain this via absurdum:

 

 

Imagine the house you want costs $1, and interest rates are 1000%. Can you afford the house? (Probably! You almost certainly have a dollar, and therefore could buy the house outright without a mortgage, thus rendering interest rates irrelevant.)

 

Imagine the house you want costs $1 billion, and interest rates are zero. Can you afford the house? (Probably not! Your monthly payment would be in the millions, which is well outside the scope of anyone who might be paying attention to me)

Now, I am well aware that there aren't any houses costing $1, there aren't any 1000% interest rates, there aren't any 0% interest rates, and if there are any houses costing $1 billion they're irrelevant to our reality.

However, these absurd examples help illustrate how it's possible for a price to be so cheap that interest rates are irrelevant, and to be so expensive that interest rates are irrelevant. Once people see this, they can see that there is in fact a range at the top and bottom of the scale (Could you buy the house outright if it cost $2? $50? $1,000? $10,000?  Would the house be unaffordable even without interest if it cost $500 million? $50 million? $5 million?)

 

Then you gradually move from absurd to reality, with the point made.