Monthly Archives: September 2020

Error help

Hey guys, I keep getting this error in grade grinder even though Boole says my sentences are correct, and I was wondering if anyone recognizes it:

“Your target sentences are wrong.  Please reread the exercise

Let me know if you’ve seen this!

Help Understanding 3.23

I struggled with sentence 3 of 3.23 until I went back and followed the example FOL translation for either/or, so I know the correct answer, but I don’t understand why that is the correct correct answer.

The sentence is: Folly belonged to either Max or Claire at 2:05 pm.

The translation was: Owned(max, folly, 2:05) ∨ Owned(claire, folly, 2:05)

Earlier the book made a point that “or” in English is sometimes an exclusive or, whereas in logic, disjunction is an inclusive or, meaning that one or both sentences are correct. In English, “Folly belonged to either Max or Claire at 2:05 pm” says to me that Folly belonged to one or the other and not both, but this remains an option in the correct FOL translation. In English-to-FOL translations, are we to assume that unless stated explicitly that both statements cannot be true, every “Either/or” is an inclusive or? Thanks in advance.

Exercise 3.18 Question

I am struggling to find a sentence that is equivalent to (a = d) without using the identity symbol. I know I need to find a sentence that can not be true of two different blocks, but I am not sure I understand how else to indicate that one block has two names. Is there another way I should be thinking about this sentence?

Homework Question

Hi Everyone,

I have a question about the homework that was due this morning at 6. For exercise 2.20 Grade Grinder kept giving me the feedback that my proof was correct but didn’t match the steps of the informal proof on page 52. When it says the proof should contain three steps matching the informal proof, I thought that would mean three steps after the Fitch line, so in addition to the three premises. Grade Grinder seems to be telling me that I shouldn’t have three non-premise steps. I’m wondering if the issue is actually about the rules I cited for each steps. Does anybody have an idea about which problem I was running up against? Thanks, Sara

Checking Homework Submissions

Good morning all,

I am posting this to the discussion board as I felt it may be helpful for others in the class. When submitting assignments in Submit is there anyway to check the progress of your submissions. In other words, is there any way to see which assignments you have submitted so far? If not, then is there any way to see If you are missing any submissions for the week? 


Olivia Reposa

Saving Tarski’s World Files

Hi everyone-
I’m not sure if this happened to anyone else, but when I was trying to save my Tarski’s sentences and worlds to my computer in order to submit them for the homework assignment, I kept getting an error message saying that I didn’t have permission. I just talked to Professor Khalifa, and apparently in order to save certain files you must first create another folder on your computer to save them into. I just created an additional folder inside of the LPL folder and saved all my work there, and that way it’s easily upload-able to the Submit program. He asked me to post this in case anyone else was having the same issues. Hope it helps!