The Prince by Niccolo Machiavelli Chapter 19 Page 5

you he can procure for himself every advantage; so that seeing on the one hand certain gain, and on the other a doubtful and dangerous risk, he must either be a rare friend to you, or the mortal enemy of his Prince, if he keep your secret.

To put the matter shortly, I say that on the side of the conspirator there are distrust, jealousy, and dread of punishment to deter him, while on the side of the Prince there are the laws, the majesty of the throne, the protection of friends and of the government to defend him; to which if the general good-will of the people be added, it is hardly possible that any should be rash enough to conspire. For while in ordinary cases, the conspirator has ground for fear only before the execution of his villainy, in this case he has also cause to fear after the crime has been perpetrated, since