Why is an oath among the conspirators unnecessary according to Brutus?

Brutus argues that an oath among the conspirators is unnecessary because he believes their cause is just and honorable. He feels that the shared commitment to their noble purpose should be sufficient to bind them together, as true honor should motivate them rather than a formal pledge. Additionally, Brutus fears that taking an oath could imply distrust among the conspirators, which would undermine their unity and resolve.