Distressed by his own personal tragedies, the Roman philosopher Cicero once asked himself whether a wise person should try to achieve the Stoic ideal of complete emotionlessness.

Cicero was distressed. He asked himself - Should a wise person try to achieve emotionlessness?

Cicero reasoned that, however desirable the goal may be, a wise person could never attain it, since emotions are not simply irrational urges.

Cicero reasoned (explained to himself) that emotionlessness cannot be attained because emotions are not simply irrational urges.

They are, rather, a product of one's estimate of the goodness and badness of the events, people, and actions one witnesses.

That they are a product of one's estimate of goodness/badness of what one sees.

Since emotions are a product of one's estimate of goodness/badness of what one sees, Cicero reasons that a wise person cannot be emotionless. This reasoning is assuming that a wise person sometimes does estimate goodness/badness of what he sees.

Assumption?
A. Wise people inevitably evaluate at least some of the things they observe.

Correct.