Marmontel assures us that never was Diderot seen to such advantage as when an author consulted him about a work. "You should have seen him," he says, "take hold of the subject, pierce to the bottom of it, and at a single glance discover of what riches and of what beauty it was susceptible. If he saw that the author missed the right track, instead of listening to the reading, he at once worked up in his head all that the author had left crude and imperfect. Was it a play, he threw new scenes into it, new incidents, new strokes of character; and thinking that he had actually heard all that he had dreamed, he extolled to the skies the work that had just been read to him, and in which, when it saw the light, we found hardly anything that he had quoted from it.... He who was one of the most enlightened men of the century, was also one of the most amiable; and in everything that touched moral goodness, when he spoke of it freely, I cannot express the charm of his eloquence. His whole soul was in his eyes and on his lips; never did a countenance better depict the goodness of the heart."[11] Morellet is equally loud in praise, not only of Diderot's conversation, its brilliance, its vivacity, its fertility, its suggestiveness, its sincerity, but also his facility and indulgence to all who sought him, and of the sympathetic readiness with which he gave the very best of himself to others.[12] It is needless to say that such a temper was constantly abused. Three-fourths of Diderot's life were reckoned by his family to have been given up to people who had need of his purse, his knowledge, or his good offices. His daughter compares his library to a shop crowded by a succession of customers, but the customers took whatever wares they sought, not by purchase, but by way of free gift. Luckily for Diderot, he was thus generous by temperament, and not because he expected gratitude. Any necessitous knave with the gift of tears and the mask of sensibility could dupe and prey upon him. In one case he had taken a great deal of trouble for one of these needy and importunate clients; had given him money and advice, and had devoted much time to serve him. At the end of their last interview Diderot escorts his departing friend to the head of the staircase. The grateful client then asks him whether he knows natural history. "Well, not much," Diderot replies; "I know an aloe from a lettuce, and a pigeon from a humming-bird." "Do you know about the _Formica leo?_ No? Well, it is a little insect that is wonderfully industrious; it hollows out in the ground a hole shaped like a funnel, it covers the surface with a light fine sand, it attracts other insects, it takes them, it sucks them dry, and then it says to them, 'M. Diderot, I have the honour to wish you good day.'"[13]