Which caution does your author note as the primary challenge to judging ethics by consequences?

It's very hard not to count one's OWN consequences more important than other consequences so our judgments are easily biased.

Considering consequences is not as noble or mature as acting on moral ideals and obligations.

Judging by consequences so often conflicts with our obligations that it can distract us from doing what is our obligation regardless of the consequences.

Judging by consequences means we are dealing only with probabilities, not certainties, about what consequences will occur.