Montesquieu wrote in the Preface of The Spirit of the Laws: "I have begun and abandoned this work [Spirit of the Laws] any number of times. On a thousand different occasions, I have taken pages and thrown them to the winds. Every day I have felt my paternal hands fail. I followed my objective, but without forming any fixed plan. I could identify neither rules nor exceptions to them; I found the truth only to lose it. But once I discovered my principles, everything I had been seeking came to me, and in the course of twenty yeas, I have seen my work begin, grow, advance, and come to its end."
Almost anyone who has ever worked on a large project can probably identify with these sentiments. But Carl L. Becker is one person who could not. Thus he accused Montesquieu of fudging "the facts." He sneeringly observed that "the 'facts' meant nothing to him until he discovered the principles which they were to illustrate." (See The Heavenly City of the Eighteenth-Century Philosophers. New Haven: Yale University Press, 1932), p. 104.) He then goes on to accuse the enlightenment philosophers on the basis of this passage that they started from general principles and not from facts, even though Montesquieu's passage shows just the opposite, namely that he wrestled with the facts until he could formulate general principles.
But there is a difference between (i) searching for the principles that might explain the facts, and (ii) seeking principles that might be illustrated by the facts. The first approach is an attempt to establish a necessary relation between facts and principles, the other approach is interested in the accidental relation of embellishment. It is important to understand this difference in one's research, even if one might also be skeptical about the possibility of the kind of explanation Montesquieu aimed at.
Becker's main thesis, namely the claim that "the philosophes demolished the Heavenly City of St. Augustine only to rebuild them with more up-to-date materials" (31) is well-illustrated, but it does not serve to explain a whole lot about the enlightenment.
Reading Montesquieu is more profitable.