Brutus It must be by his death, and for my part I know no personal cause to spurn at him But for the general. He would be crowned. How that might change his nature, there's the question. It is the bright day that brings forth the adder And that craves wary walking. Crown him that, And then I grant we put a sting in him That at his will he may do danger with. Th' abuse of greatness is when it disjoins Remorse from power. And, to speak truth of Caesar, I have not known when his affections swayed More than his reason. But 'tis a common proof That lowliness is young ambition's ladder, Whereto the climber upward turns his face. But when he once attains the upmost round, He then unto the ladder turns his back, Looks in the clouds, scorning the base degrees By which he did ascend. So Caesar may. Then, lest he may, prevent. And since the quarrel Will bear no color for the thing he is, Fashion it thus: that what he is, augmented, Would run to these and these extremities. And therefore think him as a serpent's egg— Which, hatched, would as his kind grow mischievous— And kill him in the shell.
The "common proof" that Brutus cites as a reason for killing Caesar is based on
a historic behavior of those in power
b private discussions with caesar
c evidence of caesars planned treason
d the nature of brutus childhood