Regarding Comte's “great fundamental law of the development of human intelligence,” the primary source material is vast. Substantial portions of his six-volume Cours, two massive volumes of the four-volume Système, and a number of lesser works are all concerned with the nature and applications of this three-stage law. Yet according to the received view in English-speaking circles over the past several decades, there is at bottom nothing philosophically very exciting about this law. Above all, it is said to lack empirical warrant. Even if Comte himself often calls it a “hypothesis” subject to both “historical testing” (especially in light of the actual course of maturation in the sciences) and “reasoned demonstration” (on the basis of what is “generally known about human intelligence”), and even if Mill still speaks of its “striking and instructive” general accuracy, eventually the law came to be assumed incapable of passing any rigorous efforts at confirmation – and therefore as probably never having been more in the first place than the first principle of a merely “speculative” philosophy of history. We recognize, of course, that these are the forced options of Logical Empiricism; and today, that is perhaps already enough to purchase my reconsideration of Comte's substantive idea of the law without interference from the familiar obsessions about its epistemic status. As I will argue in Part II, turning too quickly to the question of its empirical warrant obscures Comte's critically reflective use of the law; and it is this latter use that has contemporary relevance.