In all ages there have been ingenious mechanicians, excellent architects, skilful artillerymen: any error, into which it was possible for them to fall in regard to the rotundity of the earth and gravitation, in no wise retarded the development of their art; the solidity of their buildings and accuracy of their aim was not affected by it.

But sooner or later they were forced to grapple with phenomena, which the supposed parallelism of all perpendiculars erected from the earth's surface rendered inexplicable: then also commenced a struggle between the prejudices, which for centuries had sufficed in daily practice, and the unprecedented opinions which the testimony of the eyes seemed to contradict.
Thus, on the one hand, the falsest judgments, whether based on isolated facts or only on appearances, always embrace some truths whose sphere, whether large or small, affords room for a certain number of inferences, beyond which we fall into absurdity.

The ideas of St.Augustine, for example, contained the following truths: that bodies fall towards the earth, that they fall in a straight line, that either the sun or the earth moves, that either the sky or the earth turns, &c.

These general facts always have been true; our science has added nothing to them.

But, on the other hand, it being necessary to account for every thing, we are obliged to seek for principles more and more comprehensive: that is why we have had to abandon successively, first the opinion that the world was flat, then the theory which regards it as the stationary centre of the universe, &c.
If we pass now from physical nature to the moral world, we still find ourselves subject to the same deceptions of appearance, to the same influences of spontaneity and habit.