Question

In act 2.1 of The Tragedy of Julius Caesar, why do the conspirators not swear an oath?

They intend to take an oath but forget to do so.
Brutus thinks they are dishonest men and knows an oath will not mean anything to them.
In ancient Rome, the law stated that they could only take an oath if their fathers were present.
Brutus thinks that honest men will follow through on their intentions; therefore, they do not need to swear an oath.

Answer 1

Brutus thinks that honest men will follow through on their intentions; therefore, they do not need to swear an oath.

In Roman culture, you simply were true to your word. No oaths were needed, and this is the opinion the Brutus holds to. 

Answer 2

I believe the answer is: Brutus thinks that honest men will follow through on their intentions; therefore, they do not need to swear an oath.

Brutus is an idealistic man who believe that all men should act on a principle.

In the act, Brutus is depicted as someone who is against taking an oath. According to brutus, the act of taking an oath solidify the fact that the men do not have the full resolve to fulfill their promise.