PrepTest 129

Incorrect. The argument is about effective law, not obeisance. According to the argument, a law can be effective even if no one obeys it as long as it can be enforced.

Incorrect. This answer is an illegal negation of the argument, where a lack of an international police force is used to justify that law not being effective.

Incorrect. The argument can work even with other differences between the two—there are almost certainly crimes that are only relevant in an international context, for instance.

Incorrect. The argument relies on police to back up law to make it effective, but that doesn't have to be their primary purpose for the argument to work, just a purpose.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Effective law → Backed up by enforcement
Police power to enforce law → Effective law
No international police force
Therefore: International law is not effective law

Answer Anticipation:
The argument creates some conditional relationships about what makes a law effective before reaching a conclusion that a certain type of law is ineffective, so we need to take the contrapositive of that first conditional to get a rule that will allow the conclusion to be drawn:

not Backed up by enforcement → not Effective law

That second conditional, in raising something that's sufficient to establish a law is effective, doesn't play into the conclusion, so we should ignore that—using it to justify the conclusion would be an illegal negation.

With our conditional in mind, we can see that, to establish international law isn't effective law, it must be established that international law isn't backed up by enforcement. What the premise establishes instead is that there is no international police force. So in order to justify this conclusion, those ideas need to be connected—that international law can't be backed up by enforcement without an international police force.

Answer Explanation:
This answer choice connects the two ideas that need to be connected for the argument to work. If something other than an international police force could effectively enforce international law, then the lack of that police force wouldn't guarantee international law is ineffective. If some other means of backing it up is present outside of that police force, international law might be effective.

Key Takeaway:
When an argument includes conditional logic, get it to align with the conclusion if possible. From there, you can see where the gap is in the application of that conditional in reaching the conclusion. Frequently, the argument will treat a premise that doesn't trigger the sufficient condition as if it does so—as we saw here—and so the correct answer will connect that premise to the sufficient condition.