I am searching for two opposite words in philosophy of science to describe two opposite approaches in physics. To illustrate what I am searching for I will use statistical physics and particle physics as examples.

One can say that statistical physics is fundamentally based on particle physics: it means that if you simulate a system of particles in a supercomputer knowing all the fundamentals laws you will find statistical physics as an emergent phenomena.

Consequently you can have 2 types of opposite approaches: the first one corresponds to start from macroscopic behaviors and search for the fundamental laws (from statistical physics to particle physics), the second one corresponds to start from fundamental laws and search for emerging behaviors (from particle physics to statistical physics).

Question: What is the name of these two approaches in epistemology?

(I think that the first one corresponds to "reductionism" but I am not sure.)

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    emergentism? emergent properies ‘arise’ out of more fundamental entities and yet are ‘novel’ or ‘irreducible’ with respect to them
    – user6917
    Jan 25, 2015 at 4:29
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    @MATHEMATICIAN, fileunderwater both those comments should be answers, and either could be correct. Jan 26, 2015 at 15:56
  • @ChrisSunami Sure, it just felt a bit short and underdeveloped. Jan 26, 2015 at 19:37
  • There is no opposite of Reductionism, just like there is no opposite of 'down'. Down is the privileged direction. It's down all the way down.
    – Scott Rowe
    Jun 11, 2022 at 12:28

5 Answers 5


Just a short suggestion, but Holism is often taken as the opposite to reductionism, but I'm not sure if it is fully applicable in this physics example. That complex systems and their emergent properties are considered irreducible is often a characteristic of holistic approaches, in the sense that higher level processes cannot be understood by only studying their constituent parts.

However, in your first example ("from statistical physics to particle physics") you seem to be aiming for an approach that start at a macroscopic level, but then tries to find the underlying "laws", which implies reducibility. In that case, Holism isn't a suitable term. Actually, the approach you are describing is more similar to first identifying empirical/phenomenological patterns and then trying to recreate these patters using bottom-up reductionist models, which is a pretty common approach to science (simultaneously looking at macroscopic patterns and trying to explain these using lower-level mechanistic models).

  • You are claiming that there are systems which don't have an underlying general cause? Nov 27, 2018 at 14:02

The concept of supervenience seems related to these considerations -- the thermodynamic (statistical) properties of a system supervene upon the microscopic details of the atoms and their interactions.

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    Supervenience is not so much the opposite of reductionism as reductionism light. As Dupre puts it:"Supervenience inherits the metaphysical spirit of reductionism... the microscopic determines the macroscopic... if this dependency is not to be wholly mysterious, there is presumably some set of facts that could be known that would permit the inference of the macroscopic from a sufficient knowledge of the microscopic. Perhaps we could not, even in principle, know these facts. But God, I suppose, would need merely to exist in order to know them".
    – Conifold
    Nov 27, 2018 at 8:29

You are considering an example from thermodynamics and statistical physics.

The reductionist approach aims on deriving properties of a system 1. from properties of its components and 2. from the interaction of these components. In physics the study of system properties like temperature and pressure of an ideal gas are studied by thermodynamics. Statistical physics derives these system properties bottom-up from Newtonian mechanics applied to the single molecules and from an certain ansatz about the interaction of the molecules. But it does not aim to investigate the fundamental laws from studying macroscopic behaviour. Because the fundamental laws of Newtonian mechanics have been known much earlier.

Your supercomputer example gains more and more importance in physics. It aims at simulating the system behaviour bottom-up from tentative laws and parameters. After comparing the result of the simulation with the observed behaviour one adjusts the parameters - and possibly the laws too. E.g., this approach is followed by the simulation of galaxy formation. It has been previously applied with great success to the process of star development.

Probably one can name the two approaches "first top-down" and the other "first bottom-up". Both approaches go in both directions, but in different order.


The typical name for this is Emergentism which can be described as the idea that the whole is greater (or at least different) than the sum of the parts, or as described by Wikipedia:

In philosophy, emergentism is the belief in emergence, particularly as it involves consciousness and the philosophy of mind, and as it contrasts (or not) with reductionism. A property of a system is said to be emergent if it is in some sense more than the "sum" of the properties of the system's parts.


Both of the approaches you are describing are reductionist, as in both cases, you are assuming that statistical physics (SP) reduces to particle physics. Given this, you are really asking two separate questions.

Question: What is the name of these two approaches in epistemology?

On the difference between the top-down approach (from SP to PP) vs the bottom-up approach (from PP to SP), what is at play here is not whether one approach is reductionist and the other isn't, as I mentioned above, they are both reductionist.

Instead what is at play here is the logic of discovery used:

  • The top-down case, starting with SP and deriving PP, is an A Priori, Rationalist approach to discovery: In this approach, your starting point is a pre-existing theory of statistical physics, and you are making some assumptions about particle physics. The challenge is then to reconcile these pre-existing theories by trying to find the bridge laws (or bridge principles) that tie the two theories together. It is a priori (Latin for beforehand) because you are assuming that statistical physics is true before hand, now you just seek to confirm it. For the same reason it is rationalist, in the sense that assumes the truth of a fundamental idea that is independent of reason, namely that statistical physics must be in some way reconciled with particle physics, and the challenge lies in confirming this idea experimentally. This approach to scientific discovery was supported, among others, by William Whewell, see the SEP and Wikipedia articles on him for more on this approach.
  • The bottom-up approach you describe is closer to an Empiricist approach to scientific discovery: An empiricist would try to make no assumptions at all, or as little as possible about theories, and instead would be guided by only the experimental data that is available. The bottom up approach you describe is more empiricist because in this case the scientists makes no assumptions about what his/her statistical physics theory should look like. Instead, having confirmed the basic laws of particle physics, they would try to derive the laws of statistical physics strictly through logic and experimental verification. It is essentially an a posteriori (Latin for after the fact) method.

To summarize, the top-down approach would be a priori and closer to rationalist and idealist conceptions of scientific discovery, and the bottom-up approach would be a posteriori, and closer to empiricist conceptions of scientific discovery.

What is the opposite of the reductionist approach?

The opposite of reductionism is emergentism or emergence, the view that some physical and natural properties can never be reduces to more fundamental laws. For example, some hold the view that psychology can never be reduced to neuro-science, or that biology can never be reduced to chemistry. This is independent of the direction of the explanation one is trying to develop: Whether you start from the laws of chemistry and then try to integrate them into laws of biology, or whether you start with the laws of biology and try to break them down to the laws of chemistry doesn't matter. An emergentist believes that you will never be able to explain one in terms of the other. The whole is different from the sum of the parts.

  • Every human being should have to memorize what this post is saying. (And believe it)
    – Scott Rowe
    Jun 11, 2022 at 12:32

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