From Chekhov's Letters (2.15.1890)

    Did you really not like the "Kreutzer Sonata"? I don't say it is a work of genius for all time, of that I am no judge; but to my thinking, among the mass of all that is written now, here and abroad, one scarcely could find anything else as powerful both in the gravity of its conception and the beauty of its execution. To say nothing of its artistic merits, which in places are striking, one must be grateful to the novel, if only because it is keenly stimulating to thought. As one reads it, one can scarcely refrain from crying out: "That's true," or "That's absurd." It is true it has some very annoying defects. Apart from all those you enumerate, it has one for which one cannot readily forgive the author--that is, the audacity with which Tolstoy holds forth about what he doesn't know and is too obstinate to care to understand. Thus his statements about syphilis, foundling hospitals, the aversion of women for the sexual relation, and so on, are not merely open to dispute, but show him up as an ignoramus who has not, in the course of his long life, taken the trouble to read two or three books written by specialists. But yet these defects fly away like feathers in the wind; one simply does not notice them in face of the real worth of the story, or, if one notices them, it is only with a little vexation that the story has not escaped the fate of all the works of man, all imperfect and never free from blemish.