was on the train home from Berlin to Vienna, galvanized by
one of his periodic “congresses” with his eccentric friend Wil-
helm Fliess. During the long journey, Freud began drafting a
“psychology for neurologists”: his Project for a Scientific Psy-
chology.TheProjectcontains no narrative details concerning
hysterical patients and no feats of deduction like those Freud
gives us in the Studies on Hysteria.Here Freud employs his
neurological knowledge by developing a model of the mind.
(Freud began his career studying the gonads of eels; his back-
ground in hard science led to a neurological study of aphasia
before his development of psychoanalysis.)
Freud focuses on the difference between the internal and
external cases of stimulation: between being struck by a
thought or desire and being struck by something in the world
outside (light, heat, sound, and so on). Internal cases of stim-
ulus depend on memory, whereas external cases depend on
perception. By its nature, perception remains ephemeral and
ever changing. Memory, by contrast, persists, both troubling
and sustaining us. What the Song of Songs says about love and
jealousy, Freud might have remarked about memory: it is as
strong as death, and cruel as the grave.
Derrida is mainly interested in Freud’s effort to define
memory in terms of its reliance on differing quantities of
energy, or energy that occurs at different intervals. Freud tries
to explain what happens in the mind by understanding how
quantity (the amount or frequency of excitation) becomes
quality (a mental image that is empowered, or “cathected,” by
the psyche). Derrida announces enthusiastically in “Freud and
the Scene of Writing” that Freud’s Project for a Scientific Psy-
chologyis dependent “in its entirety upon an incessant and in-
creasingly radical invocation of the principle of difference”
(Writing 205 ). So Freud is already alert to the importance of
106 Writing and DifferenceandOf Grammatology