Common form of logical reasoning question

[Haleyeastham]

I am having difficulty with a similar kind of problem. Here are two examples:

Ex 1) Wealth is not a good thing, for good things case no harm at all, yet wealth is often harmful to people.

Ex 2) Most lecturers who are effective are eccentric, but some non eccentric lecturers are very effective teachers. In addition, every effective teacher is a good communicator.

Can you please help me make sense of these similar types of problems?

Thanks!

[Emily Haney-Caron]

Hi Haley,

Happy to help you with this! Could you explain a bit more about what trouble you're having? Is it difficulty diagramming/parsing them, telling the different types apart, or something else?

[Haleyeastham]

It is difficult diagramming them in order to make sense of the answer choices.

Thank you !

[Nikki Siclunov]

Hi Haleyeastham,

Diagramming conditional reasoning statements is something we cover in Lesson 2 (if you're enrolled in the Full Length LSAT class), and it's also something that The Logical Reasoning Bible discusses in Chapter Six. You can also refer to the following Blog posts on Conditional Reasoning to get a better handle on how (and when to diagram):

http://blog.powerscore.com/lsat/bid/333 ... To-Diagram

http://blog.powerscore.com/lsat/bid/288 ... Everywhere

http://blog.powerscore.com/lsat/bid/293 ... n-the-LSAT

Here's how I would diagram the conditional statements you're asking about:

Wealth is not a good thing, for good things case no harm at all, yet wealth is often harmful to people

Premise: Good Thing No Harm
Premise: Wealth Often Harmful
Conclusion: Wealth NOT a Good Thing

Since the second premise triggers the contrapositive of the first, the conclusion is logically valid:

Wealth Often Harmful NOT a Good Thing

Ex 2) Most lecturers who are effective are eccentric, but some non eccentric lecturers are very effective teachers. In addition, every effective teacher is a good communicator.

Premise: Effective Eccentric
Premise: NOT Eccentric Effective
Premise: Effective Good communicator

These premises contain Formal Logic (discussed in a virtual module under Lesson 8 in the full-length LSAT course, and also in Chapter Thirteen in the LRB). When combined, they produce the following inferences:

NOT Eccentric Good communicator
Eccentric Good communicator

It is not of paramount importance that you understand Formal Logic, as questions containing this type of reasoning are exceptionally rare these days. I'd say - focus on mastering conditional reasoning, and when you do - then think about learning how to diagram and manipulate Formal Logic problems.

Good luck!