Antedating of "Idealism"

[James A. Landau]

In a message dated Thu, 24 Mar 2005 08:13:44 -0500,  Fred Shapiro
<fred.shapiro at YALE.EDU> wrote:

>  idealism (OED 1796)
>
>  1773 Denis Diderot _An Essay on Blindness_ 50 (Eighteenth Century
>  Collections Online)  Idealism deserves very well to be reported to him;
>  and this hypothesis is as a double incentive for him, his singularity, and
>  much more the difficulty of refuting its principles, they being precisely
>  the same as those of Berkeley.

Is 1773 the date of an English translation?  I don't believe Diderot ever
wrote in English.