Psychic apparatus

The term psychic apparatus (also psychical apparatus, mental apparatus) denotes a central, theoretic construct of Freudian metapsychology, wherein:

We assume that mental life is the function of an apparatus to which we ascribe the characteristics of being extended in space and of being made up of several portions [id, ego, super-ego].

— Freud, An Outline of Psychoanalysis (1940)

As a psychologist, Sigmund Freud used the German terms psychischer Apparat and seelischer Apparat, about the functioning of which he elaborates:

We picture the unknown apparatus, which serves the activities of the mind, as being really like an instrument constructed of several parts (which we speak of as 'agencies'), each of which performs a particular function, and which have a fixed, spatial relation to one another: it being understood that by 'spatial relation'—'in front of' and 'behind', 'superficial' and 'deep'—we merely mean, in the first instance, a representation of the regular succession of the functions.

— Freud, The Question of Lay Analysis (1926)

Freud proposed the psychic apparatus as solely a theoretic construct explaining the functioning of the mind, and not a neurologic structure of the brain:

It is a hypothesis, like so many others in the sciences: the very earliest ones have always been rather rough. 'Open to revision', we can say in such cases ... the value of a 'fiction' of this kind ... depends on how much one can achieve with its help.

— Freud, The Question of Lay Analysis (1926)

Moreover, in emphasizing the immateriality of the psychic apparatus, Freud dismissed the matter of its physical substance:

That is not a subject of psychological interest. Psychology can be as indifferent to it as, for instance, optics can be to the question of whether the walls of a telescope are made of metal or cardboard. We shall leave entirely to one side the material line of approach.

— Freud, The Question of Lay Analysis (1926)