y they are of the attention of serious men, who are able to
measure the difference between a wise and beneficent use of
intelligence, and a foolish and wasteful misuse of it. "When I turn my
eyes," he says, "to the works of men, and see the cities that are built
on every side, all the elements yoked to our service, languages fixed,
nations civilised, harbours constructed, lands and skies measured--then
the world seems to me very old. When I find man uncertain as to the
first principles of medicine and agriculture, as to the properties of
the commonest substances, as to knowledge of the maladies that afflict
him, as to the pruning of trees, as to the best form for the plough,
then it seems as if the earth had only been inhabited yesterday. And if
men were wise, they would at last give themselves up to such inquiries
as bear on their wellbeing, and would not take the trouble to answer my
futile questions for a thousand years at the very soonest; or perhaps,
even, considering the very scanty extent that they occupy in space and
time, they would never deign to answer them at all."

II.

In 1769 Diderot composed three dialogues, of which he said that, with a
certain mathematical memoir, they were the only writings of his own with
which he was contented. The first is a dialogue between himself and
D'Alembert; the second is D'Alembert's Dream, in which D'Alembert in his
sleep continues the discussion, while Mdlle. Lespinasse, who is watching
by his bedside, takes down the dreamer's words; in the third, Mdlle.
Lespinasse and the famous physician, Bordeu, conclude the matter.[213]
It is impossible, Diderot said to Mdlle. Voland, to be more profound and
more mad: it is at once a supreme extravagance, and the most
deep-reaching philosophy. He congratulated himself on the cleverness of
placing his ideas in the mouth of a man who dreams, on the ground that
we must often give to wisdom the air of madness, in order to secure
admittance. Mdlle. Lespinasse was not so complacent. She made D'Alembert
insist that the dialogue should be destroyed, and Diderot believed that
he had burned the only existing copy. As a matter of fact, the
manuscript was not published until 1830, when all the people concerned
had long been reduced to dust. There are five or six pages, Diderot said
to Mdlle. Voland, which would make your sister's hair stand on end. A
man may be much less squeamish than Mdlle. Voland's sister, and still
pronounce the imaginativ