When we need to form our own estimates of others, we should learn to trust our own judgments, and not be swayed by the criticisms or slanders of others. Behavior is better verified by observation, rather than by the rumors and innuendos of others.
An amusing illustration of this principle is found in an anecdote related by Valerius Maximus (III.8.ext.6) about Alexander the Great. The great king was enjoying some leisure in Cilicia after a great victory over Darius. On a certain day the weather happened to be very hot, so he decided to take a swim in the river Cydnus. Shortly after this, he began to experience muscle pains and partial paralysis, to the extent that he was not able to walk of his own accord. His men were greatly worried about him, knowing that their fortunes were entirely dependent on him. He was taken to bed and his lieutenants called doctors in an effort to find out what the problem was; after some deliberation, one of the doctors (Philippus by name) made a medicinal liquid for the king to drink.
At about the same time that Philippus was offering the medicine to Alexander, a messenger arrived from one of Alexander’s generals, Parmenio. The messenger bore a letter warning Alexander that the doctor Philippus had been bribed to administer poison to the king. When Alexander read the letter, he did nothing; he accepted the cup from Philippus, drained it, and then handed the doctor the letter he had just received. Alexander had such confidence in the people around him that he trusted his own judgment about the doctor.
While this behavior may seem unnecessarily reckless, the story does contain an element of truth: we should not be too willing to accept the testimony of slanderers, gossips, or rumor-mongers. This was the point that Petrarch was trying to make in a letter to Niccola Acciaiuoli in which he counseled his friend against being too eager to listen to informers:
Let him banish suspicions, deny the use of his ear to informers, brush back those who get too insistent, and punish those who refuse to stop such behavior. As the words of one emperor said: “A prince who does not discipline informers, empowers them [princeps qui delatores non castigat, irritat].”
In the vast majority of cases, we are better off not knowing malicious rumors, whether they are said about someone else or about us. They do nothing but poison the mind. It was for this reason that Julius Caesar is said to have burned an entire chest of letters written by his political opponents that came into his possession. He felt that reading such material would poison his mind and prevent the kind of reconciliation he hoped to build after he had secured his victory. This proved to be a wise step: for some things we are better off not knowing.