This simulated LSAT question has been provided by Blueprint LSAT Prep. Because LSAC rules prohibit the use of actual LSAT questions on the internet, this question has been written by Blueprint founder Trent Teti and tests a type of argument that frequently appears on the LSAT. This week’s installment: The fallacy of composition.
Kelly likes chocolate more than any other food in the world. Local restaurant Risby’s uses chocolate in its quiche, so it’s certain that Kelly will like Risby’s quiche.
The reasoning in the argument is flawed because it:
(A) inappropriately takes for granted that because Kelly likes one aspect of the quiche, he’ll like the entire quiche
(B) justifies a generalization on the basis of one example
(C) attempts to compare two quantities that are not comparable in any way
(D) assumes that because someone currently likes chocolate, then he will in the future
(E) inappropriately relies on the opinions of experts
What to do
First, read the prompt. At Blueprint, we label this type of question a “flaw” question because you’re searching for the flaw in the argument. Reading the prompt first and classifying it lets you know what you’re looking for in the stimulus. In this instance, we know we’re dealing with a flawed argument, so you should actively search for the conclusion and premises in the argument, as well as keeping an eye out for the flaw being committed.
Conclusion and premises
In this case, the conclusion is that it is certain that Kelly will like Risby’s quiche. The premises, or support, for the argument is that Kelly likes chocolate more than any other food in the world. Hurray for Kelly. He’s clearly hit the jackpot by finding out about Risby’s quiche. Or has he?
Evaluating the argument
While it’s true that Kelly likes chocolate more than any other food in the world, the quiche at Risby’s isn’t entirely made of chocolate – it’s likely it’s just one ingredient of many. There may be eggs, peppers, and other ingredients that Kelly hates. In other words, just because Kelly likes one ingredient in the quiche, that doesn’t mean that he’s necessarily going to like the quiche as a whole.
The fallacy of composition
This flaw is known as the fallacy of composition and it crops up fairly often on the LSAT. Just because one part of the quiche (chocolate) has a certain property (tasting good to Kelly) doesn’t mean that the whole (the entire quiche) has the property of the part (tasting good to Kelly).
Whenever an argument on the LSAT posits that because something has a property, its part must have those properties, or that because a part of something has a property, then the whole must have that property, keep an eye out for the fallacy of composition.
The answer choices
(A) is the correct answer because it properly identifies the flaw. Just because Kelly likes one aspect of the quiche (chocolate), this doesn’t mean he’ll like the entire quiche. (B) is incorrect because, while the argument does justify a generalization (that Kelly will like Risby’s quiche based on his liking chocolate), this is not the flaw in the argument. (C) is incorrect because the quantities are comparable (both involve chocolate), so this is not the flaw. (D) describes a temporal fallacy that does occur on the LSAT, but is not the flaw in this argument (E) like (D), (E) describes a fallacy that does occur on the LSAT, but because the argument does not appeal to an authority, it is not the flaw for this particular argument.
There you have it, LSAT studiers. Remember to be careful of arguments that use a part to justify a whole, or vice versa. We would also advise against any chocolate quiches, from Risby’s or elsewhere.
Simulated LSAT question by Blueprint founder Trent Teti. Blueprint provides 100-hour live LSAT courses throughout the US and our newest online course, Blueprint: The Movie 2.0 with hand-drawn animation delivered via high-definition video.