Question 157 and all unless conditions

[sanarda]

I can not understand how to set up the unless condition

The sandwich will have G unless it has T.
-T -> G. T is sufficient and G is necessary. This seems backwards to me.

Confused

[timmydoeslsat]

The sandwich will have G unless it has T.

With unless statements, do this:

1) Realize that unless introduces a necessary condition.

The part before unless is the sufficient condition. This sufficient condition must be negated.

The sandwich will have G unless it has T.

~G ---> T

Contrapositive of that is:

~T ---> G

Let us take note of what happens when an unless statement is structured in such a way that it does not have anything coming before the word unless:

Unless it has T, the sandwich will have G.

We know that unless introduces a necessary condition and that we do not negate what is given to us. What comes after that, in this case, is the sufficient condition, of the sandwich having G. This part will be negated.

~ G ---> T

Contrapositive:

~ T ---> G

Do you understand unless statements now?

[sanarda]

Yes! That is a little clearer. I just have to train my brain... Unless introduces the necessary statement. The sandwich will have G unless it has T. It the necessary condition (T) negates G.

So -G -> T. sufficient -G Necessary T. I think I have it.. Lets hope I can Keep it..

Contrapositive -T -> G

Unless it has T, the sandwich will have G.
We have not been given anything to take away until we get to our sufficient condition (G) therefore we cannot negate "Unless we have T" because we don't know if T is there or not. What we do know is that if T is there (necessary) we will not have G (Sufficient). -G -> T

-T -> G

Thanks so much

[sw]

I am NOT understanding how to write this, and I'm not understanding where I am going wrong.

1) What am I missing?
2) Do we really write the equation differently when the order of the statement's two clauses is reversed? That doesn't make sense to me.

The sandwich will have G (normal state) unless it has T (interrupter of the normal state)
Unless it has T, the sandwich will (always) have G
-T -> G (If T hasn't shown up yet, then the normal state of G still applies)
-G -> T (If normal state G disappeared, then it must be because T is there)

But I also think I should write it this way:
G -> -T
(If G is still around, then T must not have shown up.)

I'm still confused by how to write this.

[ROBDEPASQUALE]

These answers are just awful. And they haven't changed in over a year. Aren't there any newer questions?

¬Pleased

[pcirka1]

I have been struggling with this exact same issue. It feels to me like when 'unless' is involved, it creates mutual exclusions so that the arrow can go either direction.

From Kaplan:

"He will go to the mall unless it rains."

If ~R --> M and if ~M --> R

Fine. I have no issues with the above.

But based on the original statement, I cannot for the life of me understand why its NOT true that:

"If it rains, we know for sure he does not go to the mall".