A paradigm (from gr. paràdeigma, model) is a scientific framework and it is used to define the main characteristic of science in a specific period.
Thomas Khun, in his “The Structure of Scientific Revolutions”, explains that a paradigm changes when there is a crisis in the previous one. This crisis is the result of the discovery of new events that can’t be explained through the previous paradigm. Then there is a scientific revolution and this means change in the dominant paradigm.
In C18th there was a scientific revolution with represented by Bacon, Cartesio and Newton. This was the period of the paradigm known as mechanistic-reductionist. The certainty that properties of each phenomenon are perceptible is the main characteristic of this model. Accordingly matter is objective and that is why we can observe it. The principle of this framework is a deterministic one: the principle of cause and effect.
In C20th there is a crisis in the mechanistic paradigm as quantum theory appears. Observation becomes an active variable to explain the scientific phenomena. Events can’t be observed alone, but only in their contexts.
A new paradigm originated from this scientific revolution. Systemic-holistic or biopsychosocial paradigm is the scientific framework of present science and of PCA.
Phenomena can be observed only by looking to their totality. The human being is a complex system and has to be studied together with larger and lesser systems. One of the main peculiarity of this paradigm is its interdisciplinary approach. According to this peculiarity the representatives of this paradigm are scientists, research workers, philosophers and intellectuals from different fields.
In this paradigm there is a new way to look at health.
“Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity” (World Health Organization, 1948)