The Greek term cathexis (?) was chosen by James Strachey to render the German term Besetzung in his translation of Sigmund Freud's complete works. Freud himself wrote of "interest (Besetzung)", in an early letter to Ernest Jones.
Peter Gay objected that Strachey's use of cathexis was an unnecessarily esoteric replacement for Freud's use of Besetzung - "a word from common German speech rich in suggestive meanings, among them 'occupation' (by troops) and 'charge' (of electricity)".
Freud defined cathexis as an investment of libido, pointing out for example how dream thoughts were cathected with different amounts of affect. A cathexis or emotional charge might be positive or negative, leading some of his followers to speak as well of a cathexis of mortido. Freud called a group of cathected ideas a complex.
Freud frequently described the functioning of psychosexual energies in quasi-physical terms,[need quotation to verify] representing frustration of libidinal desires, for example, as a blockage of (cathected) energies which would eventually build up and require release in alternative ways. This release could occur, for example, by way of regression and the "re-cathecting" of former positions or fixations, or the autoerotic enjoyment (in phantasy) of former sexual objects: "object-cathexes".
Freud used the term "anti-cathexis" or counter-charge to describe how the ego blocks such regressive efforts to discharge one's cathexis: that is, when the ego wishes to repress such desires. Like a steam engine, the libido's cathexis then builds up until it finds alternative outlets, which can lead to sublimation, reaction formation, or the construction of (sometimes disabling) symptoms.
M. Scott Peck distinguishes between love and cathexis, with cathexis being the initial in-love phase of a relationship, and love being the ongoing commitment of care.
Freud saw the early cathexis of objects with libidinal energy as a central aspect of human development. In describing the withdrawal of cathexes which accompanied the mourning process, Freud provided his major contribution to the foundation of object relations theory.
Freud saw thinking as an experimental process involving minimal amounts of cathexis, "in the same way as a general shifts small figures about on a map".
In delusions, it was the hypercathexis (or over-charging) of ideas previously dismissed as odd or eccentric which he saw as causing the subsequent pathology.
Critics charge that the term provides a potentially misleading neurophysiological analogy, which might be applicable to the cathexis of ideas but certainly not of objects.
Further ambiguity in Freud's usage emerges in the contrast between cathexis as a measurable load of (undifferentiated) libido, and as a qualitatively distinct type of affect - as in a "cathexis of longing".