See if you can figure this one out…
Since Miley Cyrus would never date a boy who did not believe in marriage, and anyone who truly understands romance believes in marriage, only a boy who truly understands romance would have any chance of dating Miley Cyrus.
The reasoning in the argument is flawed because the argument ignores the possibility that some people who
(A) have no chance of dating Miley Cyrus do not truly understand romance
(B) truly understand romance have no chance of dating Miley Cyrus
(C) truly understand romance do not believe in marriage
(D) believe in marriage have no chance of dating Miley Cyrus
(E) believe in marriage do not truly understand romance
Read on for the explanation and answer…
This is a great example of a flaw LSAT question with formal logic or conditional reasoning. You’re looking to identify what’s wrong with the argument but first you’ll need to breakdown the conditional reasoning. Let’s start by drawing out our basic if-then statements:
We start with a couple of premises:
“Since Miley Cyrus would never date a boy who did not believe in marriage…”
“anyone who truly understands romance believes in marriage”
With any LSAT question involving conditional reasoning you want to turn the statements into basic IF-THEN statements. Our premises then become:
IF a boy does not believe in marriage THEN he cannot date Miley Cyrus
IF you understand romance THEN you believe in marriage
You can represent these graphically as follows:
Usually you would use just the letters B and D or BM and DM to represent belief in marriage and dating Miley Cyrus but we’ve used the full words here for ease of explanation. When you do this yourself on the actual or practice LSAT exams you should use only a single letter, it will speed things up.
These two IF-THEN statements are our premises and are known to be true for sure. We then have our conclusion which is suspect as it makes a conclusion that cannot be drawn on the basis of the two premises provided.
Our conclusion is a bit tricky as it’s an “ONLY IF” statement. The easy trick for these statements is to remember that you reverse the order of the statement when you turn it into a basic IF-THEN statement. e.g. ONLY IF A THEN B becomes
IF B THEN A or IF B –> A
Our conclusion was “only a boy who truly understands romance would have any chance of dating Miley Cyrus” or in IF-THEN terms:
ONLY IF understand romance THEN date Miley Cyrus
and reversing that to a basic IF-THEN statement we get:
IF Dating Miley Cyrus THEN understand romance
We can represent this graphically as:
So now we have our premises and conclusion expressed as IF-THEN statements. You can answer the question from here or you can go on to add some additional information by taking the contra-positives of each IF-THEN statement. For a detailed explanation of how to set up the contra-positive and IF-THEN statements check out this article, or try our LSAT Prep Course Online.
So here’s our complete story including contra-positives:
So what’s wrong with our conclusion? Our conclusion starts with the information on the left side of the IF THEN statement. Which is either “If you are dating Miley Cyrus” or from the contra-positive “If you don’t understand romance”
Let’s start with the first one: “If you are dating Miley Cyrus” – what do we know about someone who is dating Miley Cyrus? The way to find out is to skim read down the left side of all your equations in the premises. The premises are our facts so what we have there is known to be true. We skim the left side for something about a person “dating Miley” and we can then follow it to the right to find out more information. So we find the statement:
So we can conclude that if you’re dating Miley Cyrus, you believe in marriage. But our conclusion takes this further and concludes that you also understand romance. Can we go this far? You can find out by continuing to follow the chain of logic in your premises, we’ve gone from dating Miley, to believing in marriage – what next? Nothing comes next! We have no statement that starts with belief in marriage on the left side and so we can draw no conclusions on this basis. So our conclusion went to far. It should have stopped with “Anyone who dates Miley Cyrus must believe in marriage.” and not gone on to conclude they also understand marriage. So the error here is that the argument assumes that if you believe in marriage you also understand romance, or in other words and in the words of our question stem, it ignores the possibility that some people who believe in marriage do not truly understand romance.
With the information in our premises it’s possible that we have someone who dates Miley, believes in marriage but does not truly understand romance. This possibility was overlooked or ignored and so (E) is our correct answer.