Reductionism is any of several related philosophical ideas regarding the associations between phenomena which can be described in terms of other simpler or more fundamental phenomena. It is also described as an intellectual and philosophical position that interprets a complex system as the sum of its parts.
In this world dominated by scientific and technological change, which threatens to drag it towards a new posivitism, another more fundamental doubt is raised. Having subdued nature by using his reason, man now finds that he himself is as it were imprisoned within his own rationality; he in turn becomes the object of science. The "human sciences" are today enjoying a significant flowering. On the one hand they are subjecting to critical and radical examination the hitherto accepted knowledge about man, on the grounds that this knowledge seems either too empirical or too theoretical. On the other hand, methodological necessity and ideological presuppositions too often lead the human sciences to isolate, in the various situations, certain aspects of man, and yet to give these an explanation which claims to be complete or at least an interpretation which is meant to be all-embracing from a purely quantitative or phenomenological point of view. This scientific reduction betrays a dangerous presupposition. To give a privileged position in this way to such an aspect of analysis is to mutilate man and, under the pretext of a scientific procedure, to make it impossible to understand man in his totality. One must be no less attentive to the action which the human sciences can instigate, giving rise to the elaboration of models of society to be subsequently imposed on men as scientifically tested types of behavior. Man can then become the object of manipulations directing his desires and needs and modifying his behavior and even his system of values. There is no doubt that there exists here a grave danger for the societies of tomorrow and for man himself. For even if all agree to build a new society at the service of men, it is still essential to know what sort of man is in question. (Papal Writings, 14 May 1971).