profundity means the quality of seeing to the heart of subjects,
Rousseau had in a general way rather less of it than the shrewd-witted
crusher of the Infamous. What the distinction really amounts to is that
Rousseau had a strong feeling for certain very important aspects of
human life, which Voltaire thought very little about, or never thought
about at all, and that while Voltaire was concerned with poetry,
history, literature, and the more ridiculous parts of the religious
superstition of his time, Rousseau thought about social justice and duty
and God and the spiritual consciousness of men, with a certain attempt
at thoroughness and system. As for the substance of his thinking, as we
have already seen in the Discourses, and shall soon have an opportunity
of seeing still more clearly, it was often as thin and hollow as if he
had belonged to the company of the epigrammatical, who, after all, have
far less of a monopoly of shallow thinking than is often supposed. The
prime merit of Rousseau, in comparing him with the brilliant chief of
the rationalistic school of the time, is his reverence; reverence for
moral worth in however obscure intellectual company, for the dignity of
human character and the loftiness of duty, for some of those cravings of
the human mind after the divine and incommensurable, which may indeed
often be content with solutions proved by long time and slow experience
to be inadequate, but which are closely bound up with the highest
elements of nobleness of soul.

It was this spiritual part of him which made Rousseau a third great
power in the century, between the Encyclopædic party and the Church. He
recognised a something in men, which the Encyclopædists treated as a
chimera imposed on the imagination by theologians and others for their
own purposes. And he recognised this in a way which did not offend the
rational feeling of the times, as the Catholic dogmas offended it. In a
word he was religious. In being so, he separated himself from Voltaire