Certain preliminary conditions were required, and these were not fulfilled till the seventeenth century.

So long as men believed that the Greeks and Romans had attained, in the best days of their civilisation, to an intellectual plane which posterity could never hope to reach, so long as the authority of their thinkers was set up as unimpeachable, a theory of degeneration held the field, which excluded a theory of Progress.

It was the work of Bacon and Descartes to liberate science and philosophy from the yoke of that authority; and at the same time, as we shall see, the rebellion began to spread to other fields.
Another condition for the organisation of a theory of Progress was a frank recognition of the value of mundane life and the subservience of knowledge to human needs.

The secular spirit of the Renaissance prepared the world for this new valuation, which was formulated by Bacon, and has developed into modern utilitarianism.
There was yet a third preliminary condition.

There can be no certainty that knowledge will continually progress until science has been placed on sure foundations.