Intuitive understanding of "unless"

[SorJuana]

HI everyone, I apologize in advance if this is not the right place to ask this question!

I've just recently started studying for the LSAT and I'm trying to pay special attention to conditional reasoning to make sure I have a rock-solid understanding of it since it is so central to many aspects of the LSAT. One thing that I am trying to do is not just have a mechanistic understanding of conditional reasoning, but to truly, intuitively, fundamentally understand it. One particular concept which has been tripping me up quite a bit is the word "unless" when used in conditional reasoning. Now, I understand that when I see the word unless, I can mechanistically use the "Unless Equation" that the PowerScore Bibles teaches and I would correctly diagram whatever sentence I'm looking at.

However, recently I was trying to independently arrive at the correct diagram for an "unless" sentence without simply resorting to blindly applying the equation. I used the following sentence:

"I will go to the park unless it is raining"

I was thinking about this phrase and what I thought the correct diagram should be, I got a little stuck. To me, when I hear that phrase, intuitively, what it means is that if it is not raining, then I will go to the park. Which, according to the "Unless Equation", is the correct diagram for the phrase: (¬R-->P). However, this would mean that the diagram (P-->¬R) is incorrect. Which means that, if I said the above phrase, I could still go to the park even if it is raining. However, to me, intuitively, that is exactly the one thing the phrase "I will go to the park unless it is raining" is saying will NOT happen.

Strangely enough, when I try to just reason my way through the diagram of another conditional statement with the word unless (e.g. "I will fail unless I get an A"), I don't really run into any sort of trouble and can correctly create the appropriate diagrams in the sort of story-telling fashion I used above. "I will fail unless I get an A" means that if I don't get an A, I will fail, but that if I fail, it doesn't necessarily mean I didn't get an A because there could be other ways to fail, etc. Therefore the correct diagram is (¬A-->F) and not (F-->¬A)

I guess I'm just confused what I am missing when thinking through the rain/park example. Is there another, more illuminating way I should think of the phrase "I will go to the park unless it rains" in my head? Where exactly is my intuition leading me astray?

P.S. My one thought is that I should think of "I will go to the park unless it is raining" as "If it doesn't rain, I will definitely go to the park." Then it sorta makes sense because then my intuition tells me that "not raining" is one condition that will, with 100% certainty, trigger me going to the park, but I could possibly not mind going to the park even if it rains. Then the correct diagrams ensue. Is this how I should think of the original statement?

[SorJuana]

Oh no, I apologize, I think I tripped myself up as I was writing this post and diagrammed what I meant incorrectly(which is really only emblematic of my difficulties understanding conditional reasoning).

Correction: When I hear "I will go to the park unless it rains", I intuitively think that means that if it rains, I will not go to the park. But the diagram (R-->¬P) is incorrect according to the unless equation. If I try to intuitively think about the statement, the correct diagram of (¬P-->R) also makes sense, since if I had said that statement and I didn't go to the park, then it must've rained.

How should I be thinking about the original statement, what intuitions are helpful and which should I discard because they are clearly tripping me up?

[Rachael Wilkenfeld]

Hi SorJuana,

Glad you asked. These conditional statements can be complicated to think through, and often we need to hone our intuition a bit as we learn how to use them.

Turning to the statment you gave originally "I will go to the park unless it's raining" we'd diagram that as park raining. One way to sort of train your intuition is to translate these statements into other words. The easiest of these for me is always the classic "if--->then."

If I'm not at the park, then it's raining.

That feels like a match to me.

Another way to think about it is more of a story sort of way. I think that's what you were aiming for with your intuition. Honestly, I worry that turning it into a story is too likely to lead you astray. It's tempting because you think you are understanding it better. But it's important to use those conditional reasoning indicators as a guide because your intuition could be more about what you expect to occur than what the stimulus says will occur. The LSAT makers love to write a situation that feels like it should be one way, but actually is technically different. The reason we use these sorts of equations and tools is to avoid falling into those traps.

Let's look at why using your example.

a) I will go to the park unless it's raining.
b) If it's raining, then I will not go to the park.

Using natural language, those FEEL the similar. But they are two different conditional statements describing two different scenarios. Your original (statement a) tells us that if you are not at the park, we know it's raining. The trigger there is your absence at the park. It can also be helpful to think about what we don't know based on the conditional. Here, we don't know what happens when it's raining. It's possible to go to the park. It's possible not to. If we want to tell a story about it, we could talk about Nature Loving Nick. He goes to the park as much as possible. In snow. In hail. In the hottest part of summer. He goes all the time, unless it's raining. He hates going in the rain because he hates the smell of rain. So, if he's not at the park, we know it's raining. Otherwise, he'd be there. In fact, even in the rain, he might still show up. If he's gone though, we are SURE it's raining.

The second statement (statement b) has a different trigger. There the trigger is the rain. Once we know it's raining, we know you won't go to the park. We don't know what happens when you don't go to the park in this situation. It could be because it's raining. It could be because you don't like parks. We only know here that if it's raining, you won't be going. Here we can think about Comfortable Cam. Cam hates being wet. Or cold. Or too warm. Really, Cam prefers a nice climate controlled room. So, if it's raining, we know Cam won't go to the park. It's also possible he won't go when it's not raining. He might hate parks all around. But our knowledge is limited to when it's raining.

So intuition is problematic here, because you likely would find one of those two people more sensible. Your brain could interpret those conditionals in either way using intuition, but they are two different conditionals with two very different meanings. They both describe situations that can occur in the real world. LSAT writing is meant to confuse you a bit. We use the various equations and indicators to help us avoid getting trapped. I will say too that this is something real logicians do. They translate language into symbols to make it easier and more clear to work with.

Hope that helps!
Rachael