If mental causation exists, then mental phenomena would affect the bodies of sentient beings.

Then the bodies of sentient beings (and only they) would be affected by an additional set of causal phenomena compared to all other physical things.

Since a cause affects its effect, it should be possible to distinguish between sentient bodies and non-sentient things, based on their physical properties.

But this is not the case. Merely by inspecting a phenomenon physically, we cannot know whether it is affected by mental phenomena or not.

Hence, mental phenomena cannot affect physical phenomena.

  1. Is this a good argument?
  2. Is it related to some well-known philosophic argument?
  • 2
    The inference from "merely by inspecting a phenomenon physically, we cannot know" to "it is not possible to distinguish" is invalid regardless of what the two are applied to. Just because we cannot do it right now does not mean that it is impossible. It may even be possible for us eventually, and even if not, we are only human. Compare to philosophical zombies, who are empirically indistinguishable from conscious creatures despite having no consciousness. Mental causation can be just as undetectable. At least, by us.
    – Conifold
    Sep 9, 2023 at 16:02
  • 1
    Consider if one never physically learned how to speak a foreign word, can the same one mentally cause one's mouth to speak the said word? If one had physical paralytic stroke can the same one mentally cause one's arm to move freely? Also maybe the existence of somnambulists who do many things in their sleep which they would not venture to do when awake consciously is much easier and more powerful for your physical causal closure argument?... Sep 9, 2023 at 23:03
  • @Conifold if you convert your comment to an answer, I will accept the answer
    – Sam
    Sep 10, 2023 at 10:47
  • 1
    Your argument itself is solid known as causal closure principle yet your reasoning is weak. Sure we can only observe physical things not private mental states if they really exist, and there's a famous philosophical problem of other minds which sounds silly colloquially but profound. Descartes famously proposed mental causation and many monistic non-dual physicalists or idealists critiqued such idea. Cause is problematic here since it alone sufficiently determines its effect, while it only correlates especially when you're in above situations... Sep 12, 2023 at 6:42
  • 1
    @Sam Everything outside of our light cone is undetectable by us according to relativity, but there are, presumably, suns and planets there. If there are fundamental fields that do not interact with matter we are made of - the same.
    – Conifold
    Sep 14, 2023 at 19:32

3 Answers 3


Merely by inspecting a phenomenon physically, we cannot know whether it is affected by mental phenomena or not.

I would argue that one sticking point in your argument lies around the use of "cannot know" here. There is a range of logical consequences with absolute certainty to those of no certainty. And yet you seem confident we cannot know in any way. This is dubious; so let us creates the counter question for you to wrestle with:

Why do you believe you are justified in claiming we cannot know if some physical object is part of our ontological domain of the mental?

Let's take a practical example. It is non-controversial to suspect that people with brains can think. Therefore, in the hypothetical a spacecraft slams into the surface of the earth and we pry it open and find a tiny green being just like in the movies. It has eyes, ears, and digits on its arms and legs. The government whisks away the crash and the ostensible pilot and dissects the latter at which point it is determined the being has a comparable version of peripheral and central nervous system.

In fact, its brain seems to resemble ours with a brain stem, and structural similarities to our own: a corpus callosum, a limbic system, a neocortex, and four major lobes corresponding to our own. Histologists further determine though the tissue has many irregularities such as non-iron mechanism of gaseous transport and genes that appear to not align with the tree of life, what are absolutely functionally equivalent are the neurons in the brain.

But beyond the anatomical and physiological evidence, there is also the craft itself. It is made of advanced metallurgical processes. It was tracked by NORAD entering the atmosphere and crashing demonstrating non-natural maneuvers such as attempting to recover a viable trajectory. It has what appears to be glyphs typical of a language. In no possible world would an observer believe this craft is a non-artifact.

So, obviously, for those of us who reject the zombie hypothesis as the product of bad thinking and refusing to accept the premise of embodied cognition, we would we make the following argument:

P1: Any human being with a brain would obviously almost certainly be capable of being associated with phenomenological experience.
P2: This non-human being seems to meet the functional criteria that human beings possess to allow us to with fair certainty establish the association including biological and technical homologues.
C: Therefore, despite never having seen this being behave as if it partook of mental life, we would nonetheless conclude it was capable and have an explanation why it didn't; it died.

Now, what this goes to show is that one has to accept that mental life has a problem with third-person validation that goes far beyond difficulty in explaining consciousness. Solving that problem is relatively easy compared to the hard problem of consciousness which is explaining metaphysically why there should be any reason to conclude that physical beings have mental lives at all, and why the signs of that life: awareness, consciousness, phenomenological descriptions, introspection, private qualia, etc. should be why they are. This is, of course, is the Chalmer's hard problem of consciousness.

  • Excellent answer, but I'd add that for someone who believes that all behavior is explainable in pure physical terms, it's not so clear we would be justified in assuming that an alien intelligence has a mental life. There is a fascinating story by Peter Watts called Blindsight that illustrates this. I'd encourage anyone interested in the philosophy of mind to read it. Sep 9, 2023 at 21:53
  • @DavidGudeman Thanks. I'll look into Watts work. en.wikipedia.org/wiki/Blindsight_(Watts_novel)
    – J D
    Sep 10, 2023 at 2:23
  • 1
    I am very confused about what your hypothetical is intended to demonstrate, how that relates to the zombie hypothesis, and how that leads to your argument. In every meaningful way I can see, your hypothetical is identical to saying "imagine we found a human from another country with a brain resembling the brains of other humans". What's the difference (apart from the fact that you replaced "human from another country" with "alien")?
    – NotThatGuy
    Sep 10, 2023 at 14:46
  • @NotThatGuy We can draw inferences about humans borne of experience that cannot be said of an extraterrestrial first contact. Hence, even if we never witness the behavior of an alien, that it has a mental life under the context above would be beyond reasonable doubt. To be explicit, the idea that we cannot use physical information to demonstrate other mental lives is a fundamentally flawed claim. As we only have physical access to other mental lives, we only and always use our empirical access to determine mental lives.
    – J D
    Sep 10, 2023 at 23:56
  • 1
    @Sam Proof is a function of one's views on evidentialism. I would suggest that inference to best explanation through both empirical and rational means would be the best approach. en.wikipedia.org/wiki/Evidentialism In any event, most beliefs are intuitional based on economical grounds.
    – J D
    Sep 12, 2023 at 18:55

As others have mentioned, an epistemic inability/failure doesn't imply an ontological impossibility.

However, as I have dared raised this elsewhere, there's actually a very prolific line of research spanning over a century showing that mind can influence physical/biological bodies in dramatic or noticeable ways. The generic phenomenon is known as psychokinesis or distance mental influence, and comes in many varieties depending on whether the target is a living thing or not, human or not, the kind of influence and circumstances.

For unfortunate reasons, this kind of research which has produced good-quality replicated results has been totally ignored or dismissed by modern academia and has been thus absent from the philosophy of mind debate, despite their huge implications.

A review by William Braud of bio-psychokinesis research can be read here. He cites controlled and responsible experiments producing positive results. And here's description of a typical experiment:

In a typical experiment of the type to be discussed, one selects a living organism and isolates it, usually at a distance, from all conventional sensori- motor or energetic influences of the "influencer." In principle, any living organism may serve as this "target." Next, one selects some readily measured aspect of the target organism's activity, objectively monitors that activity over a period of time, and generates a permanent record of that activity. It is, perhaps, desirable to choose an activity which occurs with moderate frequency or intensity and which is relatively stable over time, although this is not an essential requirement. An "influencer" then attempts to influence the organism's activity, mentally and at a distance, in a prescribed fashion and according to a predetermined (and, ideally, random) schedule. Conventional statistical methods are used to compare the organism's activity during periods of attempted mental influence with activity levels during comparable non-influence, control periods.

Edward Kelly et al. in their more general review of various kinds of PK research, among other examples, cite experiments involving an influencer attempting to arouse a target with the target's response measured by reactions of the nervous system. They cite controls and results:

Experimental methods have been designed specifically to rule out conventional explanations for any response seen in the target persons, such as suggestion or expectation, sensory cues, naturally occurring internal rhythms in the autonomic nervous system, recording errors, arbitrary selection of data, and chance. For example, the two persons are isolated in separate rooms with no sensory contact possible, experimental and control periods are randomly interspersed in an order that is automatically generated, and responses are recorded automatically. Under these general conditions, the results over numerous studies have been reasonably consistent and robust. In an overview of 19 studies conducted at three labs, Schlitz and Braud (1997) found an overall success rate of 37%, when 5% would be expected by chance (p = .0000007, effect size = .25). In a more recent and conservative meta-analysis of 37 studies, S. Schmidt et al. (2004) found a somewhat smaller, but still significant effect (p = .001 , effect size = .11) (Irreducible Mind, 230-231)

Irreducible Mind is a massive work which catalogues multiple categories of evidence from psychical research that falsify physicalism and support dualism, mental causation and survival of consciousness after bodily death. Yep, a highly ambitious, daring and controversial thesis among the modern scientific establishment but carried out meticulously and with critical scientific spirit throughout which has so far met no physicalist rebuttal and mostly disregard.

  • As a side note, if the conclusions of that work are sound, the question still arises why the effects of consciousness upon external phenomena are detectable, whereas the influence of consciousness on the brain of the person that possesses* it are not detectable.
    – Sam
    Sep 12, 2023 at 9:57
  • @Sam That's because consciousness is a private first-person experience inaccessible to outside observers and accessible only to the subject who can testify to its influence intuitively and introspectively as in the example,"I decide to raise my hand, and the thing goes up". However brain correlations unveiled by neuroscience make many people doubt whether it is the mind or brain making the influence but in distant influences where these brain correlates are absent and impossible, the mental causation can be clearly observed without any physical mediation clouding the reality.
    – infatuated
    Sep 12, 2023 at 11:17
  • Consciousness is a private first-person experience (unless telepathy is a real phenomenon). However, mental causation (affecting the physical) is not a private first-person experience. The notion that mental causation can be clearly observed with regards to external phenomena, but not with regards to the body&brain of the person with that consciousness is a very strange one...
    – Sam
    Sep 12, 2023 at 15:05
  • @Sam Even in cases of psychokinesis they don't directly observe consciousness. They only observe physiological changes in the target but they can reliably link the changes to the distant influencer because of the prior arrangements with the influencer (about when and what effects he/she is expected to make in the target).
    – infatuated
    Sep 12, 2023 at 15:23

There is no argument against mental causation. There is no question whether mental causation is real or not.

Human behaviour is mostly determined by mental processes. Most of our actions are voluntary. We have only a few spinal reflexes which are causal reactions to physical stimuli.

Besides, if mental phenomena couldn't cause physical phenomena, they wouldn't be observable, they wouldn't exist at all.

  • 2
    "[mental phenomena] wouldn't be observable", which is exactly the case. When is the last time you observed a "mental phenomenon"? All we can ever observe is physical action, and our own mental states are something we live through, not something we observe.
    – armand
    Sep 10, 2023 at 1:20
  • The physical activity caused by the mental activity can be observed. By reading your comment I can observe your thoughts. Sep 10, 2023 at 5:40
  • 1
    You make bold assertions, without supporting them by argumentation
    – Sam
    Sep 12, 2023 at 6:16
  • @Sam Can you give an example? Of course you cannot. Sep 12, 2023 at 6:59

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .