How does Cassius's diction allow him to persuade Brutus to his cause?

In many ways, Julius Caesar is a play
that is concerned with speech and how it is used to manipulate, coerce and flatter
people. Speech is a tool used by characters to get other characters to do what they
want, and there are many victims of speech used in this way, for example Caesar himself
and also Casca. One of the prime examples though, is this section of the play in Act I
scene 2 where Cassius "sounds out" Brutus and then persuades him to join the plot
against Caesar.

It is well worth examining Cassius'
strategy in how he does this. He starts of by commenting that he has noticed a change in
Brutus' regard towards him, recognising that there is something going on within Brutus.
Obviously, one of the aspects of Cassius is that he is a very good judge of character,
as Caesar goes on to recognise. He then goes on to flatter Brutus, assuring him of how
high he stands in favour with the people and the
Senate:

I
have heard

Where many of the best respect in
Rome

(Except immortal Caesar), speaking of
Brutus,

And groaning underneath this age's
yoke,

Have wished that noble Brutus had his
eyes.

Notice how subtly
Cassius introduces Caesar's name here, in parenthesis and with the sarcastic title
"immortal" to suggest an opposition. He then assures Brutus of his honesty and gives
testament to his upstanding character to encourage Brutus to believe his
words.

A key point in the discussion comes when they hear a
flourish and a shout (as said in the stage directions). Brutus, already goaded into
thought by Cassius, says:

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I do fear the
people

Choose Caesar for their
king.

This word "fear" allows
Cassius to talk about Caesar's humanity and how now he is passing himself off as
divine:

Why,
man, he doth bestride the narrow world

Like a Colossus, and
we petty men

Walk under his huge legs and peep
about

To find ourselves dishonourable
graves.

Note here again the
irony in the description of "petty men" - the juxtaposition of Cassius' description of
Caesar as just another mortal man and then this description of the God-like Caesar
obviously undercuts Caesar's divinity and draws attention again to how one man has
seized power and put others (like Brutus) under him. Note how this speech progresses by
introducing an element of jealousy and unfairness into what has
happened:

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Brutus and Caesar: what should be in that
"Caesar"?

Why should that name be sounded more than
yours?

Having introduced
(rather serpent-like) this temptation with logical reasoning, Cassius goes on to refer
to Brutus' ancestor (also called Brutus) who was involved in deposing the last tyrant of
Rome, obviously trying to goad Brutus into action by being true to his ancestors and
heritage.

Notice how when he has acheived his objective,
Cassius is self-deprecating about his talents:

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I am glad

That my
weak words have struck but thus much show

Of fire from
Brutus.

Here we have an
example of a master in persuasion - Cassius' words are anything but "weak", and he
establishes himself in this scene as a key manipulator and user of
rhetoric.