Are the concepts of reductionism and first principles the same?

Question

Are reductionism and foundationalism(first principle)the same thing, or at least highly similar even if different? The first-principles approach is the same as deducing all knowledge claims from axioms which cannot be derived from more fundamental axioms. This is the same as what we have called axiomatic inquiry, initiated by Euclid. In contrast to this, is empirical inquiry which arrives at knowledge and justifies knowledge claims on the basis of observation.

These possibly seem similar, to some extent, but how much, if at all?

Answer 1

First principles means that we take whatever knowledge there is and try to find routes from that to the principle, in an unbroken chain of logical connection. There is no a priori preference.

Reductionism favours a certain kind of knowledge and maps all other kinds of knowledge as different representations of the same.

The problems start when first principle starts to fail and discard all knowledge that does not fit the system as secondary, ie. first principle philosophy starts to become reductionist fast. That's because the existing variance of knowledge/experience does have a tendency to resist conceptual neatness.

Answer 2

It's less about what's vaguely different between those two, and more about what's commensurable or incommensurable for them. What epistemic graph theory suggests, for example (in its "semantics," which is, however, often merged with its syntax), is that reductionism could be interpreted as a specific kind of epistemic graph,^E which is structurally very similar, perhaps on some level even isomorphic to, foundationalism, which would answer your question in the affirmative on its own other level.

Alternatively, then, we might yet rank foundationalism as deeper than reductionism, in part on account of the direction-of-action: foundationalism proceeds from seeds to crowns of flowers and leaves, reductionism is a little ant crawling down the tree to see the roots. So there is a context in which it is reasonable to judge these doctrines sufficiently distinct to merit claiming the possibility of all permutations of absence and presence, here: either one is true and the other (whichever) isn't, neither is true (not always true, that is...), or both are true; so 4 options total.

Historically-speaking, for what it's worth, we should add in some of sec. 3.3 of the SEP article on the Vienna Circle:

How then can Vienna Circle philosophy be absolved of foundationalism? As noted, it is the Aufbau (and echoes of it in the manifesto) that invites the charge of phenomenalist reductionism. To begin with, one must distinguish between the strategy of reductionism and the ambition of foundationalism. Concerning the Aufbau it has been argued that its strategy of reconstructing empirical knowledge from the position of methodological solipsism (phenomenalism without its ontological commitments and some of its epistemological ambitions) is owed not to foundationalist aims but to the ease by which this position seemed to allow the demonstration of the interlocking and structural nature of our system of empirical concepts, a system that exhibited unity and afforded objectivity, which was Carnap’s main concern. (See Friedman’s path-breaking 1987 and 1992, and Richardson 1990, 1998, Ryckman 1991, Pincock 2002, 2005. For the wide variety of influences on the Aufbau more generally, see Damböck 2016.) However, it is hard to deny categorically that Carnap ever harbored foundationalist ambitions. Not only did Carnap locate his Aufbau very close to foundationalism in retrospect (1963a), but a passage in his (1930) led Uebel (2007, Ch.6) to claim that around 1929/30 Carnap was motivated by foundationalist principles and reinterpreted his own Aufbau along these lines (around the same time that Wittgenstein entertained a psychologistic reinterpretation of his own Tractatus that was reported back to the Circle by Waismann). To correct this foundationalist aberration was the task of the Circle’s subsequent protocol-sentence debate about the content, form and status of the evidence statements of science.

What this gets at is that reduction-to-sense-data, for example, has a foundationalist gist to it: observation reports of sense data purportedly being infallible and fundamental, they then go on to form (if via inductive reasoning) axioms for deductions therefrom, or more poetically of the "logical construction of objects from sense data" (in Russell's sense(!)). A reduction of macroscopic to microscopic physics, on the other hand, might not seem especially concerned with the direction of the evidence as such, or proceeds just as willingly from quantum information to biological spacetime, and then back and forth further and in more directions, etc. etc. forever and ever, amen. Now, though, we find a distinction between reductionism and foundationalism whereby the former is, in part, a subtype of the latter: sense-data/logical-construction theory, which is reductionist on account of being foundationalist to boot.

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^EOne might say: foundationalism is to reductionism what coherentism is to holism, to some extent, e.g. possibly isomorphic (see the remainder of the above).

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Further reading:

1. Tho[20], "Mechanical Philosophy: Reductionism and Foundationalism."
2. Berker[13], "Coherentism via Graphs."
3. Mullins[19], "Infinite Cycles and the Graphical Approach to Epistemic Justification."

Answer 3

The first principles approach is the same as deducing all knowledge claims from axioms which cannot be derived from more fundamental axioms. This is the same as what we have called axiomatic inquiry, initiated by Euclid. In contrast to this, is empirical inquiry which arrives at knowledge and justifies knowlegde claims on the basis of observation. Reductionism is the idea that knowledge at a higher level can be deduced from the entities and their interaction at a lower level. E.g. the claim that the properties of atoms can be deduced from the properties of molecules, the properties of cells can be deduced from the properties of molecules, .... Ultimately, the properties of human societies can be deduced from the properties of individuals. (Reducing higher levels to lower levels of organisation)

Answer 4

No.

Foundationalism is a philosophical theory, which addresses the nature of knowledge, which would be built upon a set of foundational (basic) truths(*). The opposite of Foundationalism is Coherentism, which sometimes is also called Holism, but this usage is not commonly accepted.

Reductionism is a systemic(**) approach which aims to explain phenomena by splitting the whole in parts. Reductionism is the dialectic opposite of Holism, which explains phenomena by considering the whole before the parts.

* My preferred example of foundational basic truth is that truth is true. Evidently, it is circular, evidently, it is tautological, however, it is valid; moreover, it can be the core of logic. All logic is valid while this fundamental truth is valid. If this fundamental truth breaks, all logic loses sense completely, so, all rational and all empirical truths (including science) vanish completely.

** Related to the Systems Theory. A system is a set of interrelated parts, so, basically, a system is a group of parts; from a simplistic viewpoint, you can think reductionists look for explanations in the parts, holists in the whole.