He borrowed from Schopenhauer the idea of the subconscious
[Schopenhauer was the most widely discussed philosopher in the German-speaking world in the time of R.Israel Salanter.]
And the system of R. Salanter was based on the concept of the subconscious--i.e. to read Musar in such a way that it will penetrate into the subconscious. [See letter 6 in Or Israel. he calls the subconscious there by its German name. It is not possible to imagine he did not know about this from the Gemran speaking world he was in at the time in Konigsberg.the city of Kant]
This is all good.
Where Musar went wrong is a whole different subject in itself.
Perhaps someone could devote a academic study on this subject?
Musar became "Frumkeit."
Reform Jews to them are the arch enemy, "the prime enemy" (Glavni Protivnick) as the Russians used to say about the USA.
Somehow Musar the idea that we the frum orthodox are all righteous and holy and everyone else is criminally insane.
To me this seems to indicate a slight disconnection with reality.