Philosopher: Both the consequences and the motives of human actions ha

The wording of this passage is slippery! Let's break down the second sentence of the passage, in which you will find both the philosopher's conclusion and his/her support for that conclusion:

The philosopher concludes that "to be a moral agent one must have free will."

This conclusion is supported by the assertion that "one cannot be a moral agent without desiring to conform to a principle." Logically, this means that to be a moral agent one MUST have the desire to conform to a principle.

In your analysis you've correctly identified a gap between the philosopher's conclusion and his/her support for that conclusion: how does one's "desire to conform to a principle" somehow mean they "must have free will?"

Here is the question stem:

So, we know that we are looking for a statement that MUST be true in order for the conclusion to be logically sound.

Take a look at answer choice (B):

How would this statement fit into the structure of the argument? Let's rearrange the passage to make it clear:

• SUPPORT: To be a moral agent requires the desire to conform to a principle
• ANSWER CHOICE (B): desiring to conform to a principle requires free will
• CONCLUSION: Therefore, "to be a moral agent one must have free will."

This answer choice perfectly fills in the logical gap between the conclusion and the support for that conclusion. More than that, it MUST be true in order for the argument to be logically sound. So, (B) is the assumption required by the argument.

I hope that helps!