Even going back to only 100 years ago the idea that "we are all equal" would have sounded ridiculous. As an example, we could take the accounts about the role of schools in various educational systems in Europe: it was widespread belief that the function of such institutions was to select the ἄριστοι - àristoi, from which it derives aristocracy - the best among the best. School was intentionally set up as an exclusionary institution, opposed to our "inclusive" endeavor: it was considered obvious, a "fundamental principle" even, that some people were better, in some sense or in another, than others.