June 2010 LSAT Section 4 Question 3

Unless the building permit is obtained by February 1 of this year or some of the other activities necessary for const...

Newt on June 3 at 09:25PM

"or" and "and"

Hi LSAT MAX, Why do we diagram the premise as "No building permit AND other activities not completed..." while the question stem says "OR"? I might need to revisit the SN lesson. Thank you in advance.

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Emil-Kunkin on June 11 at 12:55PM

This is where I think it pays to focus on the full meaning of the sentence rather than sticking rigidly to the diagram.

The sentence tells us that unless we do one of these two things, a third thing will not happen. that is, if they both fail to happen then we know that the third thing won't happen.

This indicates that in order for us to know it won't happen, it must be that thing 1 and thing 2 don't happen.

This gets into the idea that when we take a contrapositive ands and ors do in fact flip. You can review the sufficient and necessary lesson for that if you find it helpful, but I think it's equally helpful to focus on actually understanding the meaning of the statement.

I'd also note that unless statements are tricky, and I prefer to replace the word unless with if not. So here we are told that if not X or Y, then not Z. That means that if X and Y both fail to happen, we know Z failed to happen as well.