We have now to consider what d'Alembert intended in the Discours préliminaire à l'Encyclopédie: what were the foundations of its critique of erudition, and what had this to do with his desire to stabilise a class of gens de lettres? These questions must be explored in the light of a further generalisation: d'Alembert was by no means indifferent to history, but set up a contrast between an ideal and an actual history which led him to some remarkable historical insights. The Discours presents both a scheme of ‘l’ histoire philosophique que nous venons de donner de l'origine de nos idées', and a study of ‘l'ordre historique des progrès de l'esprit;’ and d'Alembert is clear as to the distinction between a ‘natural history’ of the human mind and the study of its development in actual or civil history, the product of contingency as well as nature:

The sharp distinction here drawn between scientific model and historical narrative heightens d'Alembert's awareness of the latter and does not tempt him to dismiss it as trivial, and Gibbon probably objected to nothing in d'Alembert's history of the enlightened mind beyond the practical implications of its epistemology.