Short background

I suppose everyone sometime ask to the mirror: what is thought? Answer requires some definitions or analogies. 'Thought is like motion', for example. But the question that leads to knowledge is the 'why', the cause of thought. You have asked by the cause of thought, I suppose.

Reading a little about Democritus, in Bertrand Russell's book History of Western Philosophy, I found that Democritus said that thought is a physical process. I wonder what is the actual point of view.

It might be an interesting problem because, if thought is a physical process, you reading and understanding and me writing are physical processes. In other words, mind would be subject to matter. That's rather unconfortable.


Are there philosophers who talk about this issue? Do you have something valuable to say about thought as a physical process -or maybe as different from physical processes?

  • 3
    As a general rule, materialists will talk about this and its problems, because their viewpoint is that there is nothing but the material world, so thus everything which exists must be a thing or process in the material world.
    – Cort Ammon
    Commented Mar 3, 2018 at 5:31
  • Thanks. I don't agree. That's not a viewpoint, I suppose, but a fact..
    – user29573
    Commented Mar 3, 2018 at 6:08
  • 2
    Obviously thought is not physical. Otherwise the tree in my head would be too heavy to think. I don't even know what it means to say that thought is physical. Democritus has a lot to answer for.
    – user20253
    Commented Mar 3, 2018 at 11:45
  • @santimirandarp It sounds like you may hold a materialist viewpoint, in which case that particular word may help you find a large number of articles regarding your question =)
    – Cort Ammon
    Commented Mar 3, 2018 at 14:52
  • If thought is not physical, what is your brain doing? Even if you take a Cartesian POV that it just connects real thoughts to more local representations of them that can influence matter, those representations are physical, and they are part of the thinking. We know that we can make people think differently (at least very temporarily) by applying magnetic or electrical forces to their brains. So the thinking isn't entirely finished at the point it becomes physical. Or we could not affect it with physical forces.
    – user9166
    Commented Mar 3, 2018 at 16:45

4 Answers 4


At least some part of thought is physical, or things like transcranial magnetic stimulation could not happen.

And modern animal behaviorism, neurology and evolutionary psychology have given us a lot of indications that many of the reasons for the ways we think can be explained in terms of survival and other aspects of biology. The first part of Dennet's Consciousness, Explained collects up a bunch of those, and points at others.

So, what is the resistance to imagining that the rest of thought can be explained by physiological processes?

The more important question isn't whether this is true. The question is whether it is relevant. Many people accept that thought is caused by complex phiological functions, but consider it an 'emergent' phenomenon.

Other examples of emergent phehomena are things like heat, acidity and molecular bonding. Each of these things has an accepted underlying explanation in a lower level of physics. And yet we cannot use that lower level explanation. There is too much complexity involved. It is nice to know that heat is explained by molecular motion, but we do not measure it that way, and we do not think about it in those terms when we do thermodynamic calculations. We think in terms of entropy, flow, conductance, etc.

Apart from theorems that tie the base cause to the basic principles through statistical mechanics, we never think about heat that way at all. We largely use principles from Carnot, someone with an entirely different underlying theory of heat, as a subtle substance.

Likewise, is it even helpful to work out the mechanics of thought? Or should we presume it will be as useful as measuring Brownian motion when you have a thermometer? The alternate view points out that we already know a lot of things about thought from an internal viewpoint. Why not use that information as our basis instead of pretending that we learn about thinking by observing others? Because we just don't.

So it makes some sense to purposely not bow to the obsession with 'objectivity' that makes us consider alternative formulations misguided. If the real information should come from inside, emergentism is just a sop to throw to materialists. It doesn't gain us anything but an illusion of peace. What is solves is a non-problem.

  • Great. Is Dennet's book too difficult to understand?
    – user29573
    Commented Mar 3, 2018 at 22:46
  • And also, what about understanding thought from neuroscience? If i am not mistaken, is the only way to try finding a "cause"
    – user29573
    Commented Mar 3, 2018 at 22:52
  • 1
    I didn't find it hard to understand. But there is so much detail that it gets really boring, really often. I had to leave it aside and come back to it over and over again to get through it. He touches on neurology and stuff, but he is trying to write for the general public, so he does not go too deep.
    – user9166
    Commented Mar 4, 2018 at 17:02

SEP’s article on consciousness may help you: look to the section about physicalists. (I likely have the interpretation wrong)

Here is the link: https://plato.stanford.edu/entries/consciousness/#PhyThe

  • 2
    Link only answers should be comments.
    – user9166
    Commented Mar 3, 2018 at 18:06

'Material' has turned out to be matter and energy, and information. Einstein unified the first two, and said thermodynamics is our best physical theory, and which involves entropy which is informational. Adding information as a fundamental quality, makes this property dualism which is a kind emergent materialism, in contrast to substance dualism which is opposite to materialism.

Reductionism is a rarely examined assumption by materialists, that everything is explainable in terms of simpler layers, down to sub-atomic. David Deutsch challenges that in The Fabric Of Reality, saying that things like computer programs which don't depend on a specific computer to run them, cannot be 'explained' by their material substrate - and by extension, minds and brains. Given that the smallest level seems to be a chaotic quantum foam, explaining everything in terms of more 'fundamental' layers clearly has limits (though superstring theory still be going there).

Emergent phenomena challenge the whole reductionist program. Aristotle saw the non-material or order-based part of a healthy functioning organisms as in a hierarchy, metabolic over material, nervous over metabolic, and mind over nerves. Each level of the hierarchy 'supervening' upon the substance of the preceding level, with causation able to act downwards. This seems very compatible with modern views like Deutsch's to me, which proposes four explanatory layers, epistemology, quantum mechanics, evolutionary biology, and computation theory. Not quite so simple a hierarchy of causes, but there is a clear echo.

  • Emergent phenomena (e.g. heat) can still be explained in terms of their base phenomena (for heat, molecular motion). That is what it means to supervene: No change above that is not traceable to a change below. (There is no effect of heat that was not caused by motion.) But the influence is not reducible. (Not all the effects of heat can be computed entirely by observing and measuring the motion) because of uncertainty, chaos and intractability. More importantly, focussing on the base phenomena hides the structure and content of the supervening one (e.g entropy) and is counterproductive.
    – user9166
    Commented Mar 3, 2018 at 17:00
  • @jobermark Self-replicating phenomena that produce order that is independent of specific substrate, represent a different kind of emergent phenomena however, where information must be treated seperately to material, which in a given instance is only an 'accidental' conveyor of bits&bytes
    – CriglCragl
    Commented Mar 4, 2018 at 17:37
  • @CriglCragl . No, there definitely are not two separate definitions for this recently derived term. It means what it means. To the degree that molecular motion only 'accidentally' communicates heat, the material world only 'accidentally' conveys information.
    – user9166
    Commented Mar 5, 2018 at 17:59
  • Maybe molecular bonds are a better example -- they create something that does not appear to be part of he QM base phenomena, that appears to create totally new information. It is utterly pointless not to talk in terms of bonds and to try to describe what is going on in terms of waves. But orbitals and therefore bonds are caused in every way by QM interference patterns. Just as any emergent phenomenon is caused, if untraceably, by its base phenomenon. It may be pointless to consider the chemistry of thought. But if thought is emergent, that still means it is materially caused.
    – user9166
    Commented Mar 5, 2018 at 18:04
  • There is no must here. It is possible, if silly and intractable, to explain the supervening phenomena in terms of the base phenomenon.
    – user9166
    Commented Mar 5, 2018 at 18:19

Democritus wrote about soul or thought atoms. He was a committed materialist. Nevertheless the most well-known presentation of his thought, Lucretious De Rerum Natura (On the Nature of Things) contains paeans to the divine - gods, Nature and the One.

Thought is physical

The problem here is the word 'is' which supposes in this context identity: that is thought is nothing more than physical and is only the physical. This need not be true. Aristotle defined men as thinking creatures. So thoughts are located in bodies and more specifically the head, and even more specifically the brain. This shows merely that there is a physical substrate upon which thoughts subsist or supervene. But this is perhaps not saying so much since this can be said of pretty much everything that we sense directly.

  • I am not sure if what is thought and the cause of it are the same question. I understand that it might be a physical process, but what you are talking is about the cause: it is caused by neurons, or something like that. But when we say it is "something",it is just a convention, supposing we are perceiving the same thing, isn't it? I am trying to understand also what is thought..
    – user29573
    Commented Mar 4, 2018 at 12:16

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