His ideas were stronger than himself; they swept him along without the power either to stay or to guide their movement.

"When I recall Diderot," wrote one of his friends, "the immense variety of his ideas, the amazing multiplicity of his knowledge, the rapid flight, the warmth, the impetuous tumult of his imagination, all the charm and all the disorder of his conversation, I venture to liken his character to nature herself, exactly as he used to conceive her--rich, fertile, abounding in germs of every sort, gentle and fierce, simple and majestic, worthy and sublime, but without any dominating principle, without a master and without a God."[21] Gretry, the musical composer, declares that Diderot was one of the rare men who had the art of blowing the spark of genius into flame; the first impulses stirred by his glowing imagination were of inspiration divine.[22] Marmontel warns us that he who only knows Diderot in his writings, does not know him at all.

We should have listened to his persuasive eloquence, and seen his face aglow with the fire of enthusiasm.

It was when he grew animated in talk, and let all the abundance of his ideas flow freely from the source, that he became truly ravishing.

In his writings, says Marmontel with obvious truth, he never had the art of forming a whole, and this was because that first process of arranging everything in its place was too slow and too tiresome for him.