Q14 - Historically, monetary systems have developed

[mitrakhanom1]

Can somebody please explain why the answer is E? I thought since this is an inference question with the phrase "must be true" the argument might have conditional logic or quantitative language.

When I read the argument, I created:

monetary systems developed--> pop centers with marketplaces

Greek cities---> marketplaces or agoraes

But I was unable to infer past this.

What should have been my thought process?

[ohthatpatrick]

Mitra! Wussup.

You are very close. You know that Inference often tests Conditionals. You found two Conditional triggers, "only" and "all". You missed one, in "never".

You symbolized your rules correctly:
Monetary system --requires--> Marketplace
[all] Greek cities ----> Marketplace

When you see conditionals, you should be thinking two (often related) things:
1. Can I chain these together?
2. What does the contrapositive look like / tell me?

Do these two you gave us chain?
These do NOT chain, because they both end with the same idea. But, you could combine them by using the contrapositive.

Didn't have a marketplace ---> No Monetary System and Not a Greek City

The reason (E) is correct is because we know that Mesopotamian Cities NEVER had marketplaces. So we know that they did NOT have a Monetary System.

It's possible to get this question right without having anticipated this idea, but it DOES point to a suggestion about reading.

Those first two sentences are the basics of logic. You get a rule and then a specific situation to apply the rule to.

Anything that's A is also B.
Paul is A.
Thus, Paul is also B

The contrapositive argument sounds like:
Anything that's A is also B
Luke is NOT B.
Thus, Luke must not be A.

So these first two sentences say
Any place that had a monetary system also had marketplaces.
But Meso's did NOT have marketplaces.
Thus, Meso's must not have had monetary systems.

They're trying to make this simple argument less obvious by starting the 2nd sentence with "they DID engage in trade!".

If you know you're doing Inference and SEE the conditional rule in the first sentence, take a sec and symbolize the rule and its contrapositive. Look specifically for THOSE terms elsewhere in the paragraph.

You'll either find ANOTHER conditional that chains to one of those ideas, or you'll find a SPECIFIC case to which you can apply your general rule.

And always write/consider contrapositives. The primary thing being tested with conditional logic is whether you understand how to think through the contrapositive. So it's worth being in the habit of always writing it. (until you get SO good at it that you think you don't need to anymore).


=== other answers ===

(A) "only" is too strong

(B) We can't say which came first, but since 'marketplaces' are the required ingredient in the first sentence, we would more likely say that MARKETPLACES led to monetary systems.

(C) Assuming these two cultures had any contact is completely speculative and out of scope.

(D) Speculating about what happens AFTER the fourth century is beyond what we were told.

(E) Correct. ~Marketplace -> ~Monetary