Freud's definition of counter-transference was a vague and unspecific one. After his death, the ambiguity and lack of clarity in his references to counter-transference led to vigorous debates and discussions attempting to provide substance to Freud's three references to the concept. He first mentioned the concept at the Nuremberg congress of the International Association of Psychoanalysis of 1910. His statement was short and directed to the analyst's response to counter-transference:

We have become aware of the 'counter-transference', which arises in [the analyst] as a result of the patient's influence on his unconscious feelings, and we are almost inclined to insist that he shall recognize this counter-transference in himself and overcome it. (Freud, 1910d, p. 144-145)

His second reference was three years later in a letter to Ludwig Binswanger dated February 20, 1913, while his third and final reference was in "Observations on Transference-Love" (1915a [1914]):

Letter to Ludwig Binswanger

The problem of counter-transference . . . is--technically--among the most intricate in psychoanalysis. Theoretically I believe it is much easier to solve. What we give to the patient should, however, be a spontaneous affect, but measured out consciously at all times, to a greater or lesser extent according to need. In certain circumstances a great deal, but never one's own unconscious. I would look upon that as the formula. One must, therefore, always recognise one's counter-transference and overcome it, for not till then is one free oneself. (letter 86f, p.112)

"Observations on Transference-Love"

For the doctor the phenomenon [the patient's falling in love with successive analysts] signifies a valuable piece of enlightenment and a useful warning against any tendency to a counter-transference which may be present in his own mind. (p. 160)

Some of the questions raised for psychoanalysts--that are applicable to therapy--after Freud's death by this ambiguity in his vague definition were (1) what exactly are the analysts' unconscious feelings and (2) can the analyst master these feelings or must they be fully resolved by being worked through psychoanalytically. As a result of this ongoing debate over the definition and therapeutic implications of counter-transference, in 1946 Melanie Klein made the announcement of her important discovery of projective identification. The concept of projective identification (projective identification: the unconscious act by which the client identifies unwanted, harmful feelings with their analyst as they separate these from themselves and manipulate the analyst who begins to demonstrate these feelings regardless of established habitual behavior patterns so that the client can view these harmful, unmanageable feelings in a context in which they are successfully managed within the identity of the analyst; a form of counter-interference) provides a mechanism by which transference (unconscious client-to-analyst feelings) occurs and by which counter-transference (unconscious analyst-to-client feelings) is triggered. Counter-transference after Klein became a valuable part of therapeutic sessions: rather than the analyst needing to recognize and overcoming unconscious feelings of counter-transference, through knowledge of the primal (primitive) communication mode of projective identification the analyst has a valuable tool for understanding the client's communications and for advancing the therapeutic objective of "reintegration in a safer and healthier way for growth and healing" (Barbara O’ Connell, "Understanding Projective Identification in Psychotherapy"). This renovation of therapeutic interaction was first introduced by Paula Heimann at the 1949 International Psychoanalytical Association conference in Zurich in a paper in which she said:

My thesis is that the analyst's emotional response to his patient within the analytic situation represents one of the most important tools for his work. The analyst's counter-transference is an instrument of research into the patient's unconscious (1950, p. 81)

Even though the definition of counter-transference has been clarified much since Freud's vague and ambiguous initial definition, when used in therapy, the concept of counter-transference (unconscious feeling), especially when coupled with instances of projective identification (separated and projected harmful and/or rejected feelings), is still controversial as to whether it should be understood as (1) something to "overcome," as Freud insisted, or as (2) a framework of therapeutic treatment incorporating the analyst's own personality. Historically, the analyst's role was to remain as much as possible a reflective surface, a mirror, for the patient's transference (which is the root of the cliche of the silent, nonparticipating psychoanalyst). Projective identification, as defined by Klein and Heimann, has brought to therapy the controversial potential of providing an altered role for the analyst as one in a position for their personality, especially his or her emotions, to be engaged in the transference/counter-transference dynamic in what might be described as a three-dimensional, reciprocating conception of the transference/counter-transference.   

Counter-transference is a reaction that develops between a patient undergoing psychoanalysis and the analyst. What occurs is that the doctor's unconscious begins to be affected by the feelings of dependency or fear or whatever the patient feels toward him/her. For instance, if a patient expresses a growing though unconscious dependency upon the doctor, then the doctor develops an unconscious emotional reaction to the patient's transference of feelings to the doctor. Sigmund Freud explains this counter-transference (the analyst's unconscious reaction) as a result of the patient's subtle influence upon the doctor's unconscious.

Dr. Carl Jung, a contemporary of Freud's, cautioned against "cases of counter-transference when the analyst really cannot let go of the patient...both fall into the same dark hole of unconsciousness." For, no one will know who is directing the psychoanalysis, Jung explains. If, for instance, the doctor feels erotic feelings for the patient, his judgments are clouded and his objectivity affected. Nevertheless, it seems that such a situation could easily occur because the relationship between client and doctor is one that is rather intimate since feelings, urges, passions, etc. are all discussed. If the patient and/or client is attractive, then the difficulty of avoiding emotional involvement is present.