Unless the residents of Glen Hills band together, the proposal to rezone that city will be approved. If it is the cit...

shunhe April 8, 2020

Hi @CRAIG-HUDSON,

Thanks for the question! So let’s think about how the word “unless” functions in everyday use. Consider the following sentence:

I will go to the grocery store and buy some milk, unless you already have.

Now, if we interpret “unless” as indicating a necessary condition, then we get the following:

I go to the grocery store and buy milk —> You already have

In other words, if I go to the grocery store and buy milk, then you already have. But this isn’t at all what this sentence means! What am I actually trying to say when I utter this sentence? Well, if didn’t go to the grocery store and got the milk, then I’m going, since there’s no milk in the house. In other words:

~You already have —> I will go to the grocery store and buy some milk

and, taking the contrapositive, we also know that if I didn’t go to the grocery store and get milk, it means you did. Thus, I like to think of X unless Y as ~Y —> X. In the example above, X = I will go to the grocery store and buy milk, and Y = You already have.

Hope this helps! Feel free to ask any other questions that you might have.

Chris-Smutny June 10, 2020

I don't understand why there was a 3 hour lecture explaining the rules for each indicator word when there's a significant level of interpretation that was involved which wasn't explained.

Success August 22, 2020

I am confused on this as well. Are you suggesting that "unless" means a necessary condition until it's worded differently in certain cases? If so, how can we identify the differences in wording?

Anna-Rogers October 2, 2020

This took me a minute to get as well, but hopefully this helps:

"I will go to the grocery store and buy milk" = X
"Unless you already have" = Y

If you negate the X and make the Y necessary, it follows the lesson we were originally giving on "Unless" and still holds true with this example in the contra-positive

Step 1: "Unless" introduces a necessary condition so the part of the sentence that follows "unless" will be the necessary condition.

Step 2: Negate the other part of the sentence and make it the sufficient condition.

Positive Argument Structure:
~X ---> Y (If I do NOT go to the store and buy milk, then you already have)

Contrapositive Argument Structure:
~Y ---> X (If you did NOT already go to the store, then I will go to the store and buy milk)

1st example from the lesson:
"A person cannot win the lottery unless she buys a ticket"
X= a person cannot win the lottery (~WL)
Y= unless she buys a ticket (BT)

Positive Argument Structure:
~X --->Y
If a person won the lottery then they bought a lottery ticket
WL ---> BT (if you negate a negative it becomes a positive)

Contra-positive Argument Structure:
~Y ---> X
If a she did NOT buy a lottery ticket, then that person cannot win the lottery.
~BT ---> ~WL

Question 27:
Unless the residents of Glen Hills band together, the proposal to rezone that city will be approved

PRBA = the proposal to rezone that city will be approved
GHBT = unless the residents of Glen Hills band together

Step 1: Make GHBT the necessary
Step 2: Negate PRBA and make sufficient

Positive:
~PRBA ----> GHBT
"If the proposal to rezone the city is NOT approved, then the residents of Glen Hills banded together"

Contra-positive:
~GHBT ---> PRBA
"if the residents of Glen Hills do NOT band together, the the proposal to rezone will be approved"

Shula July 7, 2023

Hi Anna, thank you so much for writing out your explanation! It makes soooo much sense! Otherwise the explanation video confused me with the new use of "unless."