LSAT Explanation PT 32, S4, Q11: Biologist: Humans have five fingers because

LSAT Question Stem

Which one of the following, if true, most strengthens the biologist's argument? 

Logical Reasoning Question Type

This is a Strengthen question. 

Correct Answer

The correct answer to this question is C. 

LSAT Question Complete Explanation

First, let's analyze the argument in the passage. The biologist claims that humans have five fingers because we descended from a fish with five phalanges in its fins. The biologist also states that our configuration of fingers is no more or less useful than other possible configurations, such as six fingers per hand. The conclusion of the argument is that if humans had descended from a fish with six phalanges in its fins and had six fingers on each hand, we would be just as content with that configuration.

To make this more understandable for the average layperson, think of it like this: Imagine you have a choice between two equally good ice cream flavors, chocolate and vanilla. You would be just as happy with either flavor because they are both equally delicious.

An "Evaluate" question for this argument could be: "Does equal usefulness of finger configurations necessarily lead to equal contentment with those configurations?"

Now, let's identify the question type and discuss the answer choices. The question type is Strengthen, which means we're looking for the answer choice that most strengthens the biologist's argument.

a) This answer choice states that everyone is equally content with our present configuration of fingers (five per hand). However, this does not address the relationship between usefulness and contentment, and it doesn't tell us whether we would be just as content with six fingers per hand. So, this answer choice does not strengthen the argument.

b) This answer choice talks about unequal usefulness, but the argument is focused on equal usefulness. It doesn't help us establish the connection between equal usefulness and equal contentment, so it doesn't strengthen the argument.

c) This is the correct answer. It establishes the connection between equal usefulness and equal contentment, which is the missing link in the argument. If humans are always equally content with two things of equal usefulness, then the conclusion that we would be just as content with six fingers per hand (if they were equally useful) is strengthened.

d) This answer choice addresses the perceived usefulness of our finger configuration, but it does not connect the new element in the conclusion (contentedness) with the central premise (usefulness). It doesn't help us establish the connection between equal usefulness and equal contentment, so it doesn't strengthen the argument.

e) This answer choice mentions a species of fish with six phalanges in its fins, but it doesn't address the relationship between usefulness and contentment. It doesn't help us establish the connection between equal usefulness and equal contentment, so it doesn't strengthen the argument.

In conclusion, answer choice C is the correct answer because it establishes the connection between equal usefulness and equal contentment, which is the missing link in the biologist's argument.