Recently, I, among other things, give private lessons in mathematics. This is not an advertisement, but an explanation of the author’s connection with the subject, and not historical, but acting. And now what banality I wanted to dwell this time in more detail: times are changing, and mathematics remains . For example, Euclid, but, say, Medvedev and Fursenko. And not that they could add something good to Euclid, they cannot really deduct.