Dante's knowledge is the knowledge of his time.
Science had made little advance since Aristotle--who is "the Philosopher" taken by Dante for his human guide--first laid its foundations.

It is useful, no doubt, to be able in a book like this, shaped by a noble mind, to study at their best the forms of reasoning that made the science of the Middle Ages.

But the reader is not called upon to make his mind unhappy with endeavours to seize all the points, say, of a theory of the heavens that was most ingenious, but in no part true.

The main thing is to observe how the mistaken reasoning joins each of the seven sciences to one of the seven heavens, and here as everywhere joins earth to heaven, and bids man lift his head and look up, Godward, to the source of light.

If spiritual truth could only come from right and perfect knowledge, this would have been a world of dead souls from the first till now; for future centuries, in looking back at us, will wonder at the little faulty knowledge that we think so much.