Psychology meant the study of Soul, that eternal spark which makes an individual unique. Overtime, by the mental nature of the study, the investigation reduced the process to study of the mind and its manifestations.
One manifestation of the mind being personality emerges at birth and continues for a while. Labeling one manifestation as normal and the other as personality disorder because it falls outside of the realm of normal, is limited especially when we claim that we are studying cause and effect, interactions within events, emotions, and perception.
To call one set of expression functions and the other dysfunction without any knowledge of what Soul was going through before birth and what It will do after birth is short sighted.
However, our communication and abilities within the physical world require compartmentalization.
This is where Diagnostic and Statistical Manual, DSM, enters the picture.
Five axes are used to study, categorize, and label these data.
Therapist evaluates, gathers further information through questionnaires and renders a diagnosis rendered.
Not all agree with the value of DSM. Opponents, including the National Institute of Mental Health, claim that the DSM represents an unscientific and subjective system.