In terms, reduction (LH:2), from: reduce-, meaning: “to lead back to first principles”, + -ion, meaning: "act or process", as compared to "anti-reduction" (or anti-reductionism), refers to the process of breaking a thing or process down to its basic or most fundamental components, parts, or mechanisms; the philosophy of reduction is called reductionism; practitioners of this ideology are called reductionists.
Historical examples of reduction attempts, conjectures, and or fully worked out belief systems include: all things reduced to four elements and two forces (Empedocles, 450BC); the universe reduced to "matter and motion" (Beeckman, 1625); all things reduced to matter (Meslier, 1729); thought reduced to molecular and chemical motions (Engels, 1882); the reduction of social phenomena to the laws of physics (Tarde, 1893); the reduction of the universe to mechanics (Snyder, 1903); the reduction of intelligence to small step brain mechanism operations (Wooldridge, 1968), biology reduced to quantum electrodynamics (Feynman, 1985). Lastly, the reduction of all of the social sciences and humanities down to chemical thermodynamics (Thims, 1995), pure and applied, this being classified, by some, as "ultra-reductionism", which is the focus of Hmolpedia.
The opposite of reductionism is called anti-reductionism, which is the general belief that to reduce is wrong; for example:
- “It is wrong to reduce all the multiformity of nature to pure mechanics. I see a corroboration of this in the principle law of nature which implies not the conservation of one and the same momentum but requires the conservation of one and the same amount of ‘active force’ [and] one and the same quantity of ‘motive activity’ which is far from the Cartesian idea of momentum.”
Several different brands or varieties exist, such as emergence or holism.
The opposite of reduction is called "emergence", the belief that all things cannot be reduced, per reason that certain unique properties "emerge" at certain levels, aka it supposes that certain non-reducible "emergent properties" exist. This philosophy or ideology is called "emergentism"; it practitioners are called "emergentists". Typically, emergentism is rooted in religious belief biases, anthropisms, or some type of dualism (Leibniz aside) or two natures belief.
The following are related quotes:
- “Physical science will not stop short of a reduction of the universe and all it contains to the basis of mechanics; in more concrete terms, to the working of a machine.”
- “All forms of social activity or achievement are ultimately reducible to electron-proton interactions.”
- “We warn against allowing ‘subjective feelings’ about the nature of thought to obscure the logic of the evidence. In particular, it must not be imagined that reduction of the processes of intelligence to small step mechanism operations is incompatible with the apparently spontaneous appearance of new and original ideas to which we apply such terms as: ‘inspiration’, ‘insight’, or ‘creativity’. ”
- “Since human organizations are staffed by human beings, and since human beings are biological organisms, it might be argued that my research problem is indeed biological. And since biological organisms are constructed from molecules, and those molecules from atoms, and the atoms from elementary particles—all obeying the laws of quantum mechanics—it might even be argued that research on human organizations is merely a rather baroque branch of physics.”
- “Sometimes philosophical or scientific insights come from an event that’s not very profound, like a party. I remember at Caltech: sure there were a lot of smart people around, some of my roommates and even some professors. I remember one fellow, a pompous fellow, he was saying ‘physics’ is the most basic of all the sciences. After all it’s how the universe works, right? Well, one of my housemates was a mathematician, and he wasn’t about to let that go. He said ‘all your physical laws, your quote on quote laws, are just mathematical models, applied to the real world.’ As if the real world didn’t matter too much? (It didn’t to him). And he seemed quite smug and satisfied that he had demolished this earlier statement until a philosopher, a guy who had become a philosophy major, came up and he said, ‘well look, you know Bruce, that all of your mathematical derivations come from the axioms, the fundamental premises, the basis upon which you base your formulas. And Bertrand Russell proved that those can be almost arbitrary. It’s all a matter of philosophical choice, where you start from. Philosophy is the most basic and general of things.’ And he seemed to have everybody convinced, until a psychologist said ‘but wait a minute, where does all your philosophy come from? It’s all rooted in psychology. It’s been proved long ago. Plato just manufactured all that stuff, based upon his own impulses. You could psychoanalyze him and derive it all. It’s all mental.’ At which point, a biologist came up and said ‘and where does all this mental stuff come from? It’s all in the brain, a biological organ, that evolved over time, to certain Darwinian needs. Obviously, it’s all rooted in biology.’ To which the chemist said ‘and what is biology? It’s just colloidal chemistry. I mean look down at the level of the cell, the level of the DNA, it’s all chemistry. It’s more basic than any of your convoluted organs and all that.’ At which point, the physicist said ‘are you all done now?”
- — David Brin (c.1971), “Caltech Party Conversation: Which Science is the Most Basic?” 
- “I would like to again impress you with the vast range of phenomena that the theory of quantum electrodynamics describes: It’s easier to say it backwards: the theory describes all phenomena of the physical world except the gravitational effect, the thing that holds you in your seats (actually, that’s a combination of gravity and politeness, I think), and radioactive phenomena, which involve nuclei shifting in their energy levels. So if we leave out gravity and radioactivity (more properly, nuclear physics), what have we got left? Gasoline burning in automobiles, foam and bubbles, the hardness of salt or copper, the stiffness of steal. In fact, biologists are trying to interpret as much as they can about life in terms of chemistry, and as I already explained, the theory behind chemistry is quantum electrodynamics.”
- “The reductionist attitude provides a useful filter that saves scientists in all fields from wasting their time on ideas that are not worth pursuing.”
- — Steven Weinberg (1992), Dreams of a Final Theory (pg. 64)
- “Present knowledge rests on the foundation of physics, which will be used to support our contentions herein. Accordingly, we admit the postulate that reality may ultimately be reducible to certain elementary particles. It is they eventually make up everything, from the most banal material things to the most exalted ethereal ideas. These particles, named fermions, are of two kinds: leptons and quarks. The former, of which electrons are the most prevalent example, are very antisocial in that they exist alone; while the latter are quite sociable and so are always found in groups. Quarks combine to form protons and neutrons, which make up the atomic nucleus. As the fundamental units of matter, various combinations of atoms, composed of nuclei and revolving electrons, build up all material structures, from molecules and cells, to planets and stars. In between, there is the realm of human society with its own kind of individual and collective entities.”
- — Paris Arnopoulos (1993), Sociophysics (pg. 22); 2005 edition (pgs. xlviii)
- “The ideal of the 11th/17th century physicists was to be able to explain all physical reality in terms of the movement of atoms. This idea was extended by people like Descartes who saw the human body itself as nothing but a machine. Chemists tried to study chemical reaction in this light and reduce chemistry to a form of physics, and biologists tried to reduce their science to simply chemical reactions and then finally to the movement of physical particles. The idea of reductionism which is innate to modern science and which was only fortified by the theory of evolution could be described as the reduction of the spirit to the psyche, the psyche to biological activity, life to lifeless matter and lifeless matter to purely quantitative particles or bundles of energy whose movements can be measured and quantified.”
- — Seyyed Nasr (1993), A Young Muslim’s Guide to the Modern World 
- Matter and motion – Hmolpedia 2020.
- (a) Wallis, Wilson D. (1923). “Social Science and Social Development” (pg. 154), Southwest Review, 8-9:150-.
(b) Gabriel Tarde – Hmolpedia 2020.
- Ultra-reductionism – Hmolpedia 2020.
- Alekseev, Georgij. (1978). Energy and Entropy (pg. 87). Mir.
- Emergent property – Hmolpedia 2020.
- Holism – Hmolpedia 2020.
- (a) Snyder, Carl. (1903). New Conceptions in Science (pg. #). Publisher.
(b) Anon. (1906). “Science and Socialism” (pg. 504), The Social Democrat, 10.
- Wooldridge, Dean. (1968). Mechanical Man: the Physical Basis of Intelligent Life (pg. 129) . McGraw-Hill.
- Pattee, Howard. (1973). Hierarch Theory: the Challenge of Complex Systems (pg. 3). G. Braziller.
- Brin, David. (c.1971). “Caltech Party Conversation: Which Science is the Most Basic?” (YT), C.A. Brin, 2010.
- Feynman, Richard. QED: the Strange Theory of Light and Matter (pgs. 7-8). Princeton University Press.
- Reductionism (quotes) – GoodReads.com.
- Hossenfelder, Sabine. (2020). “What is Reductionism?” (YT), Sabien Hossenfelder, Apr 9.
- Reduction – Wikipedia.