That the knowledge at which geometry aims is knowledge of the eternal, and not of aught perishing and transient.
That, he replied, may be readily allowed, and is true.
Then, my noble friend, geometry will draw the soul toward truth, and create the spirit of philosophy, and raise up that which is now unhappily allowed to fall down.
Nothing will be more likely to have such an effect.
Then nothing should be more sternly laid down than that the inhabitants of your fair city should by all means learn geometry. Moreover, the science has indirect effects, which are not small.
Of what kind? he said.
There are the military advantages of which you spoke, I said; and in all departments of knowledge, as experience proves, anyone who has studied geometry is infinitely quicker of apprehension than one who has not.
Yes, indeed, he said, there is an infinite difference between them.
Then shall we propose this as a second branch of knowledge which our youth will study?
Let us do so, he replied.
And suppose we make astronomy the third—what do you say?
I am strongly inclined to it, he said; the observation of the seasons and of months and years is as essential to the general as it is to the farmer or sailor.
I am amused, I said, at your fear of the world, which makes you guard against the appearance of insisting upon useless studies; and I quite admit the difficulty of believing that in every man there is an eye of the soul which, when by other pursuits lost and dimmed, is by these purified and reillumined; and is more precious far than ten thousand bodily eyes, for by it alone is truth seen. Now there are two classes of persons: one class of those who will agree with you and will take your words as a revelation; another class to whom they will be utterly unmeaning, and who will naturally deem them to be idle tales, for they see no sort of profit which is to be obtained from them. And therefore you had better decide at once with which of the two you are proposing to argue. You will very likely say with neither, and that your chief aim in carrying on the argument is your own improvement; at the same time you do not grudge to others any benefit which they may receive.
