Phenomenology is an approach to psychological subject matter that has its roots in the philosophical work of Edmund Husserl. Early phenomenologists such as Husserl, Jean-Paul Sartre, and Maurice Merleau-Ponty conducted philosophical investigations of consciousness in the early 20th century. Their critiques of psychologism and positivism later influenced at least two main fields of contemporary psychology: the phenomenological psychological approach of the Duquesne School (The Descriptive Phenomenological Method in Psychology), including Amedeo Giorgi and Frederick Wertz; and the experimental approaches associated with Francisco Varela, Shaun Gallagher, Evan Thompson, and others (embodied mind thesis). Other names associated with the movement include Jonathan Smith (Interpretative Phenomenological Analysis), Steinar Kvale, and Wolfgang Köhler. Phenomenological psychologists have also figured prominently in the history of the humanistic psychology movement.
The experiencing subject can be considered to be the person or self, for purposes of convenience. In phenomenological philosophy (and in particular in the work of Husserl, Heidegger, and Merleau-Ponty), "experience" is a considerably more complex concept than it is usually taken to be in everyday use. Instead, experience (or being, or existence itself) is an "in-relation-to" phenomenon, and it is defined by qualities of directedness, embodiment, and worldliness, which are evoked by the term "Being-in-the-World".
The quality or nature of a given experience is often referred to by the term qualia, whose archetypical exemplar is "redness". For example, we might ask, "Is my experience of redness the same as yours?" While it is difficult to answer such a question in any concrete way, the concept of intersubjectivity is often used as a mechanism for understanding how it is that humans are able to empathise with one another's experiences, and indeed to engage in meaningful communication about them. The phenomenological formulation of Being-in-the-World, where person and world are mutually constitutive, is central here.
Difficulties in considering subjective phenomena 
The philosophical psychology prevalent before the end of the 19th century relied heavily on introspection. The speculations concerning the mind based on those observations were criticized by the pioneering advocates of a more scientific approach to psychology, such as William James and the behaviorists Edward Thorndike, Clark Hull, John B. Watson, and B. F. Skinner. However, not everyone agrees that introspection is intrinsically problematic, such as Francisco Varela, who has trained experimental participants in the structured "introspection" of phenomenological reduction.
In the early 1970's, Amedeo Giorgi applied phenomenological theory to his development of the Descriptive Phenomenological Method in Psychology in order to overcome certain problems he perceived, from his work in psychophysics, with approaching subjective phenomena from the traditional hypothetical-deductive framework of the natural sciences. Giorgi hoped to use what he had learned from his natural science background to develop a rigorous qualitative research method. Giorgi has thus described his overall project as such: "[Phenomenological psychology] is nothing like natural sciences... because its [dealing with] human experiences and human phenomena. [However] I want to be sure that our criteria is this: that every natural scientist will have to respect our method. I’m not just trying to satisfy clinicians, or therapists, or humanists, I’m trying to satisfy the most severe criterion—natural scientists... because I anticipate that some day, when qualitative research develops and gets strong, the natural science people are going to criticize it. And I want to be able to stand up and say, 'Go ahead, criticize it—but you won’t find any flaws here'."
Philosophers have long confronted the problem of "qualia". Few philosophers believe that it is possible to be sure that one person's experience of the "redness" of an object is the same as another person's, even if both persons had effectively identical genetic and experiential histories. In principle, the same difficulty arises in feelings (the subjective experience of emotion), in the experience of effort, and especially in the "meaning" of concepts. As a result, many qualitative psychologists have claimed phenomenological inquiry to be essentially a matter of "meaning-making" and thus a question to be addressed by interpretive approaches.
Psychotherapy and the phenomenology of emotion 
Carl Rogers' person-centered psychotherapy theory is based directly on the "phenomenal field" personality theory of Combs and Snygg. That theory in turn was grounded in phenomenological thinking. Rogers attempts to put a therapist in closer contact with a person by listening to the person's report of their recent subjective experiences, especially emotions of which the person is not fully aware. For example, in relationships the problem at hand is often not based around what actually happened but, instead, based around the perceptions and feelings of each individual in the relationship. The phenomenal field focuses on "how one feels right now".
- Giorgi, Amedeo. (1970). Psychology as a Human Science. New York : Harper & Row.
- Giorgi, Amedeo. (2009). The Descriptive Phenomenological Method in Psychology. Duquesne University Press: Pittsburgh, PA.
- Langdridge, D. (2006). Phenomenological psychology: theory, research and method. Harlow: Pearson.
- Varela, F.J. (1996). Neurophenomenology: a methodological remedy to the hard problem. Journal of Consciousness Studies, 3330-350.
- Seidner, Stanley S. (1989). "Köhler's Dilemma", In Issues of Language Assessment. vol 3. Ed., Stanley S.Seidner. Springfield, Il.: State Board of Education. pp. 5–6.
- Snygg, Donald and Combs, Arthur W. (1949), Individual Behavior: A New Frame of Reference for Psychology. New York, Harper & Brothers 1949
- Rogers, Carl R. (1951) Client-Centered Therapy. Boston: Houghton Mifflin.
- "Personality Theories", Boeree, C. George, Donald Snygg and Arthur Combs in Personality Theory retrieved Oct. 7, 2007