R. G. Collingwood, The Idea of History, 84-85:

The eighteenth century wished for a universal history,
a history of man: but a genuine history of man would have
to be a history of how man came to be what he is,
and this would imply thinking of human nature, [......]

It made them look forward to a Utopia in which
all the problems of human life should have been solved.

[......] The truth is that of the human mind comes to
understand itself better, it thereby comes to operate in
new and different ways. A race of men that has acquired the
kind of self-knowledge at which the eighteenth-century thinkers
were aiming would act in ways not hitherto known,
and these new ways of acting would
give rise to new moral and social and political problems,
and the millennium would be as far away as ever.