What ultimately motivates brutus to join the conspiracy?

Cassius's arguments

Explanation:

Hi, in Julius Caesar by William Shakespeare, Cassius believes that he must have Brutus as a member of the conspirators.  Brutus had a reputation of honesty and persuasive skills that Cassius knew would be needed one the assassination took place. In addition, Brutus was known for his logical, reasoning and strong oratorical skills.  

Brutus is concerned about Caesar as a result of Cassius's arguments. He thinks he's ambitious but has not really seen it.

Brutus has decided that Caesar has to die. He has nothing against him personally.  His death is necessary for the good of the people.  

true. the definition explains it: a word or phrase that modifies or qualifies an adjective, verb, or other adverb or a word group, expressing a relation of place, time, circumstance, manner, cause, degree, etc. this is a dictionary definition that i have looked up in a dictionary.