On False Opinions: Niccolo Machiavelli, Discoursi ii, 22

In the second book (of three) of The Discourses (in English) the overall scope is that of the 'expansion' of Rome. Like the first, Machiavelli picks topics from this period of the early Republican period but as he says, focuses on how Rome increased in size and rule. In his preface to this second book he furthers his case on the lessons of history.

"Men always, but not always with good reason, praise bygone days and criticize the present, and so partial are they to the past that they not only admire past ages the knowledge of which has come down to them in written records, but also, when they grow old, what they remember having seen in their youth. And when this view is wrong, as it usually is, there are, I am convinced, various causes to which the mistake may be due.

The first ... is [that] the whole truth about olden times is not grasped, since what redounds to their discredit is often passed over in silence, whereas what is likely to make them appear glorious is pompously recounted in all its details." [p. 265]

Another reason he says is that men have no reason to be afraid of, or envious of, the past. Men hate things due to fear or envy, but the past lacks the incentive to frighten or make men jealous.

If that weren't enough, Machiavelli furthers the case against false opinions in chapter 22 of this second book of his Discourses on the First Ten Books of Livy's History of Rome. After the header quoted here for ch 22, he follows with a couple of examples comparing a Roman situation with an Italian one in the early 1500's. It applies in ways to situations today, as well.

"How frequently men form false opinions has been observed and is still observed by those who happen to be witnesses of their decisions, the which, unless made by men of first-class ability, are very often the reverse of being sound. And because in corrupt republics, especially [*] in untroubled times, men of first-class ability are ousted by the envy and ambitious scheming of others, men fall back on what by a common error is judged to be good, or else by those who are seeking popularity rather than the common good. Such mistakes are discovered afterwards when things go wrong, and recourse is then had of necessity to those who in peaceful times had been, as it were, forgotten.... There sometimes occur also events about which men who have had no great experience of affairs, are easily mistaken, since such happenings have plausible features which make men believe that the outcome in such a case will be what they have persuaded themselves it will be." [p. 344]

* Like the time, he says of his own times, when Francis I, king of France thought he would be able to retake Milan, then guarded by the Swiss.
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quotes and pagination in Niccolo Machiavelli The Discourses on the First Ten Books of Livy Edited by Bernard Crick, translated by Leslie J Walker, thrird revision by Brian Richardson, Penguin Books, London, 1970, 2003