TH
1
20
A LEIBNIZIAN THEME AT THE TURN OF THE 19 CENTURY
unconscious perceptions in the human soul as proof that the soul is con-
16
stantly active.
In his response to an article by Johann Joachim Spalding on the subject
of parapraxes in the Magazin zur Erfahrungsseelenkunde, Mendelssohn, like
17
Sulzer, calls on the theory of the obscure perceptions. He links Sulzer’s
puzzle – ‘daß die Seele zweyerley verschiedene Verrichtungen zugleich,
eine durch deutliche, die andere durch dunkele Erkenntnis, sehr gut ver-
18
richten kann’ – with Christian Wolff’s distinction between ‘efficient’
‘wirksame’) and ‘inefficient’ (‘unwirksame’) ideas: the former are
designed to produce an action, and so have an effect in the body
‘organischer Anstoß’); our inefficient ideas are the purely speculative or
(
(
intellectual ones. Like Sulzer (and Spalding) before him, Mendelssohn
allows that the soul can pursue two different chains of ideas simul-
taneously – the one clear and rational, the other obscure and unconscious:
we might, for example, follow a speculative line of thought at the same
time as we play a musical instrument (MzE, I, iii, 52). Problems such as
those described by Spalding begin when an errant idea creeps into the
chain of associations between our efficient ideas, or when two or more
such ideas try to work on the same bodily organs at once in some of our
automatic processes, such as in speech (MzE, I, iii, 52–63). The efficient
ideas have a powerful influence over us precisely because they are obscure:
‘
in der Region der wirksamen Ideen k o¨ nnen die dunkelsten Begriffe eine
solche Gewalt besitzen, oder vielmehr die Begriffe, die eine so große prak-
tische Gewalt haben, sind mehrentheils undeutlich, wegen der Geschwin-
digkeit, mit welcher sie aufeinander folgen, wie bei allen Fertigkeiten und
Geschicklichkeiten der Menschen zu ersehen ist’ (MzE, I, iii, 68).
Thus far, Mendelssohn’s analysis of parapraxes has not differed signifi-
cantly from that of Sulzer: he also entertains the idea of a kind of rivalry
between our clear and obscure knowledge; like Sulzer, he is troubled by
the power of our obscure ideas to confuse and confound the soul. How-
ever, the roots of Mendelssohn’s thinking are more firmly rooted in ration-
alism than those of Sulzer; and he in fact begins his analysis of the darker
side of mental life in the Magazin by stressing that the soul is always the
16
In a letter to a Dutch nobleman on how to educate a young man in philosophy (Anweisung zur
spekul. Philosophie, f u¨ r einen jungen Menschen von 15–20 Jahren (1774)), Mendelssohn – a life-long
Leibnizian – recommends reading the New Essays in tandem with Locke’s Essay. He writes: ‘Ich
getraue mich zu behaupten, daß diese beiden Werke allein fast hinreichen, einen philosophischen
Kopf zu bilden, wenn sie mit erforderlichem Nachdenken studiret werden’ (Moses Mendelssohn,
Schriften zur Philosophie und A¨ sthetik, III, i, Berlin 1932, p. 305). Jean Paul made excerpts from the
New Essays (and from Locke’s Essay) in 1787. See G o¨ tz M u¨ ller, Jean Pauls Excerpte, W u¨ rzburg
1
988, p. 185.
1
7
‘
Psychologische Betrachtungen auf Veranlassung einer von dem Herrn Oberkonsistorialrath
Spalding an sich selbst gemachten Erfahrung, vom Herrn Moses Mendelssohn’, Magazin zur
Erfahrungsseelenkunde, I, iii, 46–75. Mendelssohn had already expressed his fascination with the
darker side of the psyche in a review of Sulzer’s Kurzer Begriff. See Moses Mendelssohn, Rezensionsar-
tikel in Briefe, die neueste Litteratur betreffend 1759–1765, Stuttgart/Bad Cannstatt 1991, pp. 91–2.
18
Sulzer, Kurzer Begriff, p. 163.
Blackwell Publishers Ltd 2001.