The term abstraction derives from the Latin abstractio which in turn takes up the Greek one of “αφαίρεσις” (aphàiresis). Conceptual abstractions may be formed by filtering the information content of a concept or an observable phenomenon (removing characteristics from something in order to reduce it to a set of essential characteristics), selecting only the aspects which are relevant for a particular subjectively valued purpose. In a generic sense abstraction is the process of thought for which an element is isolated from all the others to which it was connected and is considered as a particular object of research.
In philosophy, abstraction together with generalization is a logical method for obtaining universal concepts from the knowledge of particular objects by retaining their common characteristics and putting aside those that appear only in some. The abstractive method, known since the origins of Greek thought, was theorized and arranged by Aristotle and then taken up by Boethius and adopted by all medieval philosophy according to which there are three gradual types of abstraction:
- the physical abstraction, which omits the individual characteristics of particular objects but retains their material nature;
- mathematical abstraction, which also disregards the sensitive characteristics of matter but not the intelligible ones inherent in the extension of matter itself;
- the metaphysical abstraction which merely consider the entity as an entity, putting aside even every connotation connected to the extension.
Abstraction is also talked about in the physical-mathematical sciences when instead of resorting to the abstract concept (for example that of direction) we list the conditions for which two objects (for example the parallel straight lines) have in common precisely that concept (that is, the direction is what the straight lines have in common).
Outside of metaphysics, in which abstraction has the function of reducing the object to being only, we speak instead of generalization when thought attributes these known characteristics to all objects not only to those present but also to that past and future in the which it assumes those notes are, have been and will be present. The generalization regards in particular mathematics and physics when new symbols are introduced and new hypotheses elaborated for which the previous field of investigation is enlarged which becomes a particular research sector with respect to the larger one that now contains it. For example, relativistic mechanics is a generalization of classical mechanics.