LSAT Explanation PT 19, S4, Q22: When a planetary system forms, the

LSAT Question Stem

Knowing which one of the following would be most useful in evaluating the argument? 

Logical Reasoning Question Type

This is an Evaluate question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

First, let's break down the argument in the passage. The argument states that the chances of a planet capable of supporting life being formed are high, but the chances of a large planet like Jupiter or Saturn being formed are low. The argument then states that without the gravitational forces of Jupiter and Saturn, Earth would have been frequently struck by large comets, preventing the emergence of intelligent life. Therefore, since planetary systems are unlikely to contain large planets, the chances of intelligent life emerging on a planet are low. The conclusion of this argument is that the chances of intelligent life emerging on a planet are low.

Now let's analyze the structure of the argument. The premises are:

1. The chances of a planet capable of supporting life being formed are high.

2. The chances of a large planet like Jupiter or Saturn being formed are low.

3. Without Jupiter and Saturn, Earth would have been frequently struck by large comets.

4. Planetary systems are unlikely to contain large planets.

The conclusion is: The chances of intelligent life emerging on a planet are low.

An "Evaluate" question for this argument would be: "How likely is it that planetary systems will contain many large comets?"

Now, let's discuss each answer choice in detail:

a) Whether all planetary systems are formed from similar amounts of matter: This answer choice does not directly address the conclusion or any of the premises. The type of matter that forms planetary systems is not discussed in the argument, so this information would not be useful in evaluating the argument.

b) Whether intelligent species would be likely to survive if a comet struck their planet: This answer choice does not address the conclusion, which is about the emergence of intelligent life on a planet, not about what would happen to that life after it emerged. Knowing whether intelligent species would survive a comet impact would not help us evaluate the argument.

c) Whether large comets could be deflected by only one large planet rather than by two: This answer choice is irrelevant to the conclusion, which states that it is unlikely that a planetary system would have any large planets. The significance of one large planet versus two large planets does not affect the conclusion.

d) How high the chances are that planetary systems will contain many large comets: This is the correct answer choice. Knowing this information would be crucial in determining the validity of the argument. If there are no large comets present in a planetary system, then it would still be possible for intelligent life to emerge even without large planets. Conversely, if many large comets are present, then the lack of large planets to protect against the comets would be a significant factor against the potential emergence of intelligent life.

e) How likely it is that planetary systems containing large planets will also contain planets the size of Earth: The size of the planet on which intelligent life might emerge is never discussed in the argument, so this answer choice is not relevant to the argument.