Monthly Archives: October 2020

Quantifiers tip!

I had a little bit of a goof up when using quantifiers, so I thought I’d tell you all to make sure nobody else stumbles into this. It’s pretty simple, but it tripped me up at first.

When using two variables at the same time, do not put both variables under the same quantifier, like this: Ɐxy . Instead, make sure to use two quantifiers and have one variable per quantifier, like this: Ɐx Ɐy . Hope this helps!

6.22 Issue

Hi everyone,

I’m having an issue with problem 6.22. I can prove ¬(b=c) in step 11 by using ¬Intro and citing 3-10, but for some reason Fitch won’t give me the final check for ¬(b=c) in my goal box. Meaning, every step from 1-11 gets the green check but for some reason the proof as a whole does not. Anyone running up against this issue or have an idea about what I’m doing wrong?