How do conflicting perspectives generate tragedy and controversy in Shakespeare's Julius Caesar?

While the characters Brutus and Cassius are friends, they
often do not share perspections, a difference that effects considerable conflicts in
William Shakespeare's Julius
Caesar. 

Early in the play, Cassius persuades
Brutus that Caesar is dangerous because he seeks
power:

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 dishonorable graves.
(1.2.141-144)

He, then,
convinces Brutus to take action instead of thinking that there is nothing he can do by
telling Brutus that

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Men at some time are masters of their
fates:

The fault, dear Brutus, is not in our
stars,

But in ourselves, that we are underlings.
(1.2.145-146)

Of course,
Cassius's differing point of view, although able to persuade Brutus into joining the
assassination, has disastrous results.  For, Brutus does not take Cassius's advice to
kill Marc Antony; instead he allows Antony to speak, and the civil strife that ensues
after Marc Antony's differing perspective on Caesar persuades the Roman mob to riot, is
far worse than the reign of Julius Caesar.

During this
civil strife in which Marc Antony, Octavius Caesar, and M. Aemilius Lepidus form the
triumvirate who combat against Brutus and Cassius, the "evil that men do" continues as
Antony dispenses brutally with Lepidus as of no more worth than his
horse. Before battle, Octavius and Antony go to the field to exchange insults with
Brutus and Cassius in Act V. 

So, too, do Brutus and
Cassius continue to disagree.  When he expresses reluctance to go into battle because he
has seen signs--a superstitious reaction more like that of Brutus--such as two eagles
that have fallen and

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Gorging and feeding from our soldiers'
hands,

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Who to Philippi her consorted
us.

This morning are they fled away and
gone

And in their steads do raven, crows, and
kites

....their shadows seem

A
canopy most
fatal....(5.1.88-94)

Brutus
has argued previously that

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There is a tide in the affairs of
men

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Which, taken at the flood, leads on to
fortune; (4.3.244-245)

When
Cassius wants to wait, Brutus desires to attack.

In the
ensuing battle, the growing conflict between Antony and Octavius has been foreshadowed
by their earlier exchange about Lepidus.  When Antony tells Octavius to fight on the
right, Octavius refuses to be ordered and does not.  Antony's insults to Brutus and
Cassius also have their effect. For, Cassius takes the opportunity, then, to tell Brutus
that he was always right about Antony:

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Now, Brutus, thank
yourself!

This tongue had not offended so
today

If Cassius might have ruled
(5.1.93-94)

By not waiting
for the enemy troops to advance as Cassius has suggested, the troops of Brutus are
enervated and become defeated.  Because of their disagreements from beginning to end,
Brutus and Cassius are defeated.  And, because of his selfish intentions and
disagreements with his triumvir, Antony is isolated from Octavius.  Indeed, conflicting
perspectives have led to tragedy.