Judgement is the ability to make a decision, or form an opinion objectively, authoritatively, and wisely, especially in matters affecting action; good sense; discretion.

Discernment is the ability to see and understand people, things, or stituations clearly and intelligently.

Belief is when someone thinks something is reality, true, when they have no absolute verified foundation for their certainty of the truth or realness of something.

Seneca may have been inferring that man would rather follow someone else blindly, then follow and trust their own logic and understanding.