Help with answering the choices in 421.

[ericjmyuan]

Hello David,

Thank you for your time and effort in helping me, after some thoughts, here's what I think:

A sufficient condition is a hypothetical, and a necessary condition is a necessity that must occur from the hypothetical condition. So when analyzing a statement, if an element has the wording which suggest the hypothetical situation or the chances of when it will occur, then it is a sufficient condition.

For example: Jenny will have lots of balloons at her birthday.

Since "lots of balloon" is necessary in the event that her birthday occurs, therefore, "lots of balloon" is necessary condition, and "her birthday" is a sufficient condition.

For your example of Every employee at RiteCo has worked here for at least 5 years.

Since "has worked here for at least 5 years" is a requirement that must happen when you're an employee at RiteCo, then it is "has worked here for at least 5 years" is a necessary condition.

However, in your example question in page 127, question 3, "No robot can think,"

Here's something that I have thought, would common sense come into play as well? I can say there's a lot of other things that can't think, a robot is one of them, henceforth a robot is a sufficient condition by that logic. Or is there something that I can do more analytically? One of the suggestion that you made is that the easiest ways to see it is that the sufficient condition applies to an entire group or entity, which is what I would think of when I apply it to the question, since an absolute "No" was indicated in this question, I know that the term "robot" must be a Necessary Condition.

[Dave Killoran]

Hi Eric,

Looking good so far, but here's where you need to be careful:

Here's something that I have thought, would common sense come into play as well? I can say there's a lot of other things that can't think, a robot is one of them, henceforth a robot is a sufficient condition by that logic. Or is there something that I can do more analytically? One of the suggestion that you made is that the easiest ways to see it is that the sufficient condition applies to an entire group or entity, which is what I would think of when I apply it to the question, since an absolute "No" was indicated in this question, I know that the term "robot" must be a Necessary Condition.

The idea of common sense is dangerous (it sounds funny to say that!), because the common sense you use comes from the real world, and the LSAT world and the real world are different. Almost inevitably, when students try to impose the real world on the LSAT world, they get into big trouble. That's because the job at hand is to identify what the author said in the LSAT world, and that may not make any sense to us in the real world. Here's an example:

For the sun to shine, the rooster must crow.

In conditional terms, this statement appears as:

Sun shine rooster crow

Yet, if we think about that using common sense, it doesn't maker sense. There's no way the sun shining requires a rooster to crow! Thus, students using a real world/common sense approach end up diagramming this statement as:

Rooster crow sun shine

They do this because that makes more sense to them (and seems more likely to be true). However, that's not what the author said, and thus diagramming it in this fashion immediately leads to a missed problem. So, in short, use the indicators and the ideas of sufficiency and necessity to determine each condition. If you must use common sense, only use it if the other other avenues fail to give you any insight into the statement.

Going back to the robot statement, the way I look at is it, "What do I know about robots? Well, none of them can think. So, "robot" is the sufficient condition." Alternatively, you could ask, "What do I know about things that can't think? Do they have to be robots? No, so "can't think" isn't sufficient."

All that aside, so far I feel like you are getting the overall conditional idea locked down, and that's great news--good job!

Thanks!