Hi, Wulflov,
Thanks for the question and for pointing out a couple examples that have caused difficulty for you.
Let me get right to the heart of the matter in order I hope to clarify this issue for you. In both weaken and strengthen scenarios, we are instructed to find "which of the following,
if true, would most strengthen OR weaken the author's argument?" This is the basic task. Consider some possible new information. Find the information that would have the
greatest possible effect on the validity of the argument.
Here let's bring in your concern that the correct answers on these problems contain considerations that don't appear to be "talked about in the stimulus, and [don't] directly impact the reasoning in my mind." In fact, you should anticipate the the correct answers to weaken and strengthen questions may respectively either exploit or address issues that we may not have identified in advance. Certainly, sometimes we come up with strong prephrases that closely match the correct answer. However, we should also note that implicit in the question itself is the suggestion that there may be more than one way to strengthen or weaken an argument. After all, we're looking for what will
most strengthen or weaken the conclusion. There is a tacit hierarchy of possible ways to address flaws or assumptions in these arguments.
This principle of multiple strengths and weaknesses is evident in "strengthen EXCEPT" and "weaken EXCEPT" questions. In these scenarios, we find four possible answers that help or harm the conclusion, often in widely disparate ways and with differing degrees of effectiveness.
You might then ask what you can do to prephrase for strengthen and weaken problems for which you don't know exactly what to expect in the correct answer. A reasonable first step is to try to identify why it is that the argument is not entirely convincing. For instance, with respect to the Clovis point example, we wish to shore up the idea that Clovis points didn't originate in North America. They were first invented in Asia. What evidence do we have for this? Well, some were found in Asia. So what? Am I convinced?
You might say, well, heck, what if the ones found in Asia came back there from North America? We certainly wouldn't want that to happen. Now here's the task. How could we help out this argument, show that the ones in Asia were there before the ones in North America?
Ideally, we'd want something really cut-and-dried, like, "The tribes that invented the Clovis first invented it in Asia and then their descendants took it with them to North America." Unfortunately, this kind of ace-in-the-hole is rare in all but a few LSAT problems. Instead, we have to look for a kind of circumlocution, a way to suggest this idea without coming right out and saying it. This is what the correct answer does on this problem by stating that the Asian Clovis points found thus far have all been older.
This situation is what we'd call a
defender answer choice. This strengthen answer lessens the likelihood of an unwanted possibility.
Just to recap the thought process:
- Analyze the argument.
- Ask what issues remain that might make one question the validity of the conclusion.
- Think of one (or a couple) different ways to either address or exploit these issues.
- Expect a surprise or two.
Sometimes I get really invested in one way of strengthening an argument only to find that the correct response took an entirely different approach. Keep an open mind.
One last thought. If you are struggling wondering whether a possible answer works, consider doing a version of the Variance Test™. Think of the polar opposite of the answer choice. What if all the Clovis points in Asia were far newer than their North American counterparts? Well, geez, then this guy's argument would be a little silly. The fact that the polar opposite of this answer just kinda kills the argument is one way to see that the correct answer actually does strengthen it.
If something seems a little weird or difficult to wrap your head around at first blush, just leave that one alone. Knock out the obviously wrong answers, then return to the two or three contenders to focus on whether or not they actually are good matches for your prephrase.
I hope this helps!
