67:2:20 (+ general question about LSAT grammar) Forum

[vuthy]

PT 67 sec 2 q 20 has this conclusion:

Life on earth may have been started by microbes from Mars (my emphasis obviously)

Answers D and E talk about establishing the truth of that conclusion. Putting aside for a second some other possible problems with D and E, I wanted to know what "establishing the truth" of a "may" conclusion looks like. Would it be: (1) It is true that life on earth may have been started by microbes; or (2) It is true that life on earth was started by microbes?

Option E is a pretty solid option there if you assume, as I did, that establishing the truth of a may conclusion just means that you're establishing that it may happen. But apparently that's not the language game LSAT plays?

[bp shinners]

Option E is a pretty solid option there if you assume, as I did, that establishing the truth of a may conclusion just means that you're establishing that it may happen. But apparently that's not the language game LSAT plays?

The problem with (E) is that it says that microbial life existing on Mars isn't necessary for the conclusion to follow. However, microbial life existing on Mars is absolutely necessary to reach the conclusion that this microbial life started on Mars and moved to Earth.

As far as your question about goes, all you have to establish is that this is a possibility, so your "assumption" (in quotes because it's not one) was correct.

[vuthy]

Thanks. That is helpful. But if that's the case, what's wrong w/ D? If all that's needed to establish a truth here is that life may have started w/ the microbes, aren't C and D basically interchangeable answers? Both say that it's a claim for which justification is provided (so we can ignore that part since it's a wash). C then says it is required in order to establish the main conclusion, while D says that if true, it establishes the truth of the main conclusion. Unless the "if true" in D somehow plays a role (which I don't think it does, since it's implicit in C), then C and D seem identical to me.

Again, this ^ is all presuming that "establishing the truth" just means "establishing that X may be true." If "establishing the truth" means the stronger version -- i.e, that X is true -- then I get why D would be wrong. But your reply makes me think it's the former, not the latter. So I'm confused.

[bp shinners]

Thanks. That is helpful. But if that's the case, what's wrong w/ D? If all that's needed to establish a truth here is that life may have started w/ the microbes, aren't C and D basically interchangeable answers? Both say that it's a claim for which justification is provided (so we can ignore that part since it's a wash). C then says it is required in order to establish the main conclusion, while D says that if true, it establishes the truth of the main conclusion. Unless the "if true" in D somehow plays a role (which I don't think it does, since it's implicit in C), then C and D seem identical to me.

Again, this ^ is all presuming that "establishing the truth" just means "establishing that X may be true." If "establishing the truth" means the stronger version -- i.e, that X is true -- then I get why D would be wrong. But your reply makes me think it's the former, not the latter. So I'm confused.

(C) says that it's necessary to establish the main conclusion; (D) says that it's sufficient to establish the main conclusion. So they're not interchangeable.

It's definitely necessary to establish the main conclusion - if there was never life on Mars before there was life on Earth, then life on Earth couldn't have come from Mars.

It's not sufficient, however, to establish the main conclusion, because the astronomer also adds the info about the meteorites from Mars hitting Earth.

[vuthy]

QED.