iderot felt his way round any subject that he approached, that in
this theoretic essay he suggests the possibility of teaching the blind
to read through the sense of touch. If the _Lettre sur les aveugles_
introduced Diderot into the worshipful company of the philosophers, it
also introduced him to the penalties of philosophy. His speculation was
too hardy for the authorities, and he was thrown into the prison of
Vincennes. Here he remained for three months; then he was released, to
enter upon the gigantic undertaking of his life.

The bookseller Lebreton had applied to him with a project for the
publication of a translation into French of Ephraim Chambers's
_Cyclopaedia_, undertaken in the first instance by an Englishman, John
Mills, and a German, Gottfried Sellius (for particulars see
ENCYCLOPAEDIA). Diderot accepted the proposal, but in his busy and
pregnant intelligence the scheme became transformed. Instead of a mere
reproduction of Chambers, he persuaded the bookseller to enter upon a
new work, which should collect under one roof all the active writers,
all the new ideas, all the new knowledge, that were then moving the
cultivated class to its depths, but still were comparatively ineffectual
by reason of their dispersion. His enthusiasm infected the publishers;
they collected a sufficient capital for a vaster enterprise than they
had at first planned; D'Alembert was persuaded to become Diderot's
colleague; the requisite permission was procured from the government; in
1750 an elaborate prospectus announced the project to a delighted
public; and in 1751 the first volume was given to the world. The last of
the letterpress was issued in 1765, but it was 1772 before the
subscribers received the final volumes of the plates. These twenty years
were to Diderot years not merely of incessant drudgery, but of harassing
persecution, of sufferings from the cabals of enemies, and of injury
from the desertion of friends. The ecclesiastical party detested the
_Encyclopaedia_, in which they saw a rising stronghold for their
philosophic enemies. By 1757 they could endure the sight no longer. The
subscribers had grown from 2000 to 4000, and this was a right measure of
the growth of the work in popular influence and power. To any one who
turns over the pages of these redoubtable volumes now, it seems
surprising that their doctrines should have stirred such portentous
alarm. There is no atheism, no overt attack on any of the cardinal