Goethe, half a millennium later, was not only drawn
by the beauty of nature, but he had likewise an unquenchable
intellectual curiosity, and sought diligently to understand the
meaning of the universe in which he lived.

"No other poet has ever combined the loftiest poetry with the
discussion of such complicated topics in all branches of learning.
In one place we find a long discussion of the origin and development
of life, which, naive and scholastic as it is, shows some lines of
resemblance to the modern doctrines in biology; in another place
there is a learned discussion between the poet and Beatrice
concerning the cause of the spots in the moon, in which an actual
experiment in optics is given."

The first passage to which Professor Kuhns refers, while containing
many speculative elements, is a discussion of certain important basic
problems in biology that have always appealed to thinking men at every
period of the history of science, and never more so than in our own
day. They must still be considered undecided, though many volumes have
been written on them in the last century. There are thoughts in
Dante's exposition of the subject that are startling enough to the
modern biologist, and that make it clear how much men's minds run
along the same grooves in facing questions that we are prone to think
have occurred to men only in the last {349} few generations. The other
quotation to which Professor Kuhns refers deserves to be quoted
entire. It is perhaps even more striking because of its actual
description of an experiment in optics, which shows how much this
great poetic intelligence of the medieval time, usually supposed to be
so abstracted and occupied with things other-worldly and supernal,
living his intellectual life quite beyond the domain of sense, still
remembered the teachings of his university days, and even recalled the
details of demonstrations that he had seen. The passage occurs in the
II. canto of the Paradiso, beginning with line 97:

"Take thou three mirrors, two of them remove
From thee an equal distance, and the last
Between the two, and further from thee move;
And turned towards them let a light be cast,
Behind thy back, upon those mirrors three,
So that from all reflected rays are passed.
Then, though the light which furthest stands from thee
May not with them in magnitude compete,
Yet will it shine in brightness equally."

It is easy to un