Chapter 5, Tutorial 4
Indirect Proof: Reductio Ad Absurdum

What a name! It makes logic sound so competitive: one takes the other side's claims and shows they are so wrong as to reduce to absurdity!

Look, Joe. You say that your checking balance is positive. But you also say that your only activity since yesterday is to spend $227.50 and deposit $38. Yet you just told us that your account balance yesterday was under $170. So....what have you been smoking?

Well, you, a nicer person than me, might say...



































Let's look at a more contrived example, but one we can easily symbolize in SL.