Here we take a look at how since is used on the LSAT and how you can use it to better understand arguments in LSAT questions.

We often see “since” used in one of the following constructions. They are basically the same but reversed:

1. “Conclusion”, since “premise.”
2. Since, “premise”, “conclusion.”

So “since” is often part of a two part sentence. One part being your conclusion or sub-conclusion and the other part being a premise supporting that conclusion.

Let’s look at an actual LSAT question from the June 2007 LSAT exam:

Novel X and Novel Y are both semiautobiographical
novels and contain many very similar themes and
situations, which might lead one to suspect plagiarism
on the part of one of the authors. However, it is more
likely that the similarity of themes and situations in the
two novels is merely coincidental, since both authors are
from very similar backgrounds and have led similar
lives.
Which one of the following most accurately expresses
the conclusion drawn in the argument?

(full question and answers below)

You can see where since is used in the last sentence.

“However, it is more likely that the similarity of themes and situations in the two novels is merely coincidental, since both authors are from very similar backgrounds and have led similar lives.”

Here we have our conclusion as the first part of the sentence, followed by SINCE and then a premise which supports the conclusion directly.

Understanding this construction can help you break down the components of an argument faster.

BEWARE though, merely because we have found “a conclusion” does not necessarily mean it is “the main conclusion” of the argument.  In this case it is but in other questions this conclusion may go on to support a further conclusion. The key is to check whether this conclusion goes on to support some further part of the argument (making this a sub-conclusion) or if the rest of the argument supports this conclusion (making it the  main one).

More help with breaking down arguments in our LSAT Prep Course online.

The full questions and answers for the question above are here:

Novel X and Novel Y are both semiautobiographical
novels and contain many very similar themes and
situations, which might lead one to suspect plagiarism
on the part of one of the authors. However, it is more
likely that the similarity of themes and situations in the
two novels is merely coincidental, since both authors are
from very similar backgrounds and have led similar
lives.

Which one of the following most accurately expresses
the conclusion drawn in the argument?

(A) Novel X and Novel Y are both
semiautobiographical novels, and the two
novels contain many very similar themes and
situations.

(B) The fact that Novel X and Novel Y are both
semiautobiographical novels and contain many
very similar themes and situations might lead
one to suspect plagiarism on the part of one of
the authors.

(C) The author of Novel X and the author of
Novel Y are from very similar backgrounds
and have led very similar lives.

(D) It is less likely that one of the authors of
Novel X or Novel Y is guilty of plagiarism
than that the similarity of themes and
situations in the two novels is merely
coincidental.

(E) If the authors of Novel X and Novel Y are from
very similar backgrounds and have led similar
lives, suspicions that either of the authors
plagiarized are very likely to be unwarranted.

Correct answer: (D) This simply restates the conclusion expressed before “since” in our last sentence.

Which one of the following, if true, best resolves the discrepancy above?

A) Ring tailed lemurs eat only the hard shell of the beetles.
B) Ring tailed lemurs often kill beetles by accident.
C) Ring tailed lemurs do not kill beetles frequently.
D) Beetles often compete with Ring tailed lemurs for food sources.
E) Beetles are easily caught by Ring tailed lemurs.

Explanation:

This is a paradox question and you are looking to resolve the paradox or discrepancy. The paradox here is that despite being unable to digest meat the ring tailed lemurs are eating beetles which would seem to be meat. We are looking for an explanation for this behavior.

A) If the lemurs do not eat the meat and only eat the shell that would explain our discrepancy. They are not consuming meat, only a hard shell that may be digested by the lemur. (A) is our correct answer choice.
B) This explains why they are killing the beetles but does not address the issue of why they are eating them and so does not resolve our paradox.
C) The fact that they do not kill them frequently still does not explain why they do kill them sometimes and more so why do they eat them. We have not addressed our paradox with this answer choice.
D) Once again, this statement may explain why the lemurs kill the beetles but does not explain our paradox as to why they eat them despite being unable to digest meat.
E) The beetles may be easy to catch but if the lemurs cannot digest they meat then why are the lemurs catching and eating the beetles? This does not explain our discrepancy either.

So our correct answer and the only one that addresses the discrepancy or paradox is answer choice A. Be careful of answer choices that explain some aspect of the argument but do not address the paradox directly. A good way to avoid these common wrong answer choices is the have a clear understanding of the paradox before moving on to our answer choices. In this question we paraphrased the paradox as “despite being unable to digest meat the ring tailed lemurs are eating beetles”. With this in mind the correct answer is much easier to spot.

How does this statement differ from “Suzie is selected IF, AND ONLY IF Bob is selected”.

IF AND ONLY IF, is a biconditional statement, meaning that either both statements are true or both are false. So it is essentially and “IF” statement that works both ways.

So our statement “Suzie is selected IF, AND ONLY IF, Bob is selected” means that Suzie and Bob are either both selected or both not selected. There are a variety of standard logical symbols used to represent this relationship including:

“↔”, “⇔” and “≡”, and “iff”

For the purpose of diagramming your LSAT Logic Games we recommend the following:

Note that IF AND ONLY IF is different than simply ONLY IF.

Only If simply creates the reverse statement as if you used “IF”

So the statement “IF Mary is selected then Will is also selected” is the same as “Mary is selected ONLY IF Will is also selected” or “ONLY IF Will is select, is Mary selected”

All of which can be respresented as:

IF M –> W