The German philosopher Immanuel Kant was born in 1724 into the midst of the European Enlightenment. The Enlightenment meant different things in different countries, but certain common features can be discerned. Kant referred to the Enlightenment as European man's coming of age; the assurance with which man had known his place in the universe was being destroyed for ever. This did not mean the replacement of one doctrine by another in which man could at least find a place, no matter how unpleasant it might be; man was cast adrift in a void, there to be dependent only on his own resources. The Enlightenment questioned the right of anyone at all to claim a monopoly of truth; this throws the decision as to what is the truth back on the individual. The abandonment of authority as the source of truth leads to a profound search as to the origins and justification of our beliefs. The eighteenth century is marked by many embarking on this search full of hope, confident that human reason has the capacity to provide answers and discover truths. It led many thinkers who were intelligent and honest in their deliberations to scepticism; an inability to see how claims to human knowledge can be justified.

Developments in astronomy, with the work of Copernicus in the sixteenth century, had already begun to undermine the medieval edifice which gave man his defined place in the universe. The Great Chain of Being, with God at its summit, stones at its base, and men and angels in between, was dismembered. The Sun, not the Earth, was the centre of our planetary system, situated in a universe of unthinkable immensity and man was denied his privileged place in it.