Letters 88.13

O what marvellous skill! You know how to measure the circle; you find the square of any shape which is set before you; you compute the distances between the stars; there is nothing which does not come within the scope of your calculations. But if you are a real master of your profession, measure me the mind of man! Tell me how great it is, or how puny! You know what a straight line is; but how does it benefit you if you do not know what is straight in this life of ours?

Seneca, Letters to Lucilius 88.13, translated by Richard Mott Gummere