Introduction: The Bieri Trilemma

The mind-body problem might be the basis problem on the philosophy of mind. The philosopher and author Peter Bieri summarized it in a trilemma [1]. The trilemma consists of three propositions which many people may spontaneously agree with:

(1) Mental phenomena are non-physical phenomena.
(2) Mental phenomena can cause effects in the realm of physical phenomena.
(3) The realm of physical phenomena is causally closed.

The first proposition follows our intuition that the mind and consciousness in ourselves are basically different from things in the world outside. My mind is subjective, only immediately accessible for me, whereas things outside of my mind appear to exist objective and are perceptible for everyone. Furthermore, if mental phenomena were physical, then all my decisions would be subject to the physical law of cause and effect; thus freedom would be impossible since all my decisions would be predetermined by their causes.

The second proposition is in agreement with our deep belief that our will, thoughts, and emotions do control our body’s movements and with that our behavior. If the second proposition was not true, then my consciousness, my thoughts and feelings would be epiphenomena only, that is, resultless accompanying effects of that physical brain processes which actually control my behavior, quasi behind my back. All my thinking and feeling would be redundant and a pure self-deceit.

The third proposition means that sufficient physical causes are provided for every event in the physical world, and that every event in the physical world happens because of nothing than its physical causes. That’s a basic assumption of physics. All physical laws – the even existence of physical laws – is based on that premise, and with that all technology, namely regarding the ability to plan and predict technical processes on the basis of our knowledge of physical laws.

So there are good reasons for all of the three propositions. Now the trilemma is that only two of them can together be true:

If 1 and 2 are true, that is, if mental phenomena are non-physical, but nevertheless have impact on the physical world, then proposition 3 must be false.

If 1 and 3 are true, that is, if mental phenomena are non-physical, and the physical world is causally closed, then mental phenomena cannot impact on the physical world, an the proposition 2 is false.

Finally, if 2 and 3 are true, that is, if mental phenomena can impact on the causally closed physical world, then the must be physical, and the proposition 1 is false.

Obviously, all the three propositions cannot be true together, therefore, we have to deny on of them – but which? If one denies 1, it results in physicalism, if 2 is denied, it results in epiphenomenalism. People who deny 3 are probably dualists; some of them believe in God; for them, off course, the belief that the Spirit of God meshes with the physical world forms a natural basis for the belief that their own mind controls their body and their behavior.

All the three positions – physicalism, epiphenomenalism, and dualism – are hold today, but I think that physicalism has been on the rise in the last decades. Physicalism is consistent with both, a scientific view of the world and the strong intuition that our thoughts, feelings, and decisions control our behavior. However, physicalism also involves some problems. In my view, at least two of them are serious:

One of the serious problems was already mentioned above, in the first proposition of the trilemma: If mental phenomena are physical phenomena, then my decisions are subject to the physical law of cause and effect. That is, from a cause (or a constellation of causes) necessarily results a certain effect. Physical causes cannot choose what results from them – we, by contrast, believe we can choose between different options of behavior in a given situation. Apparently, that belief is inconsistent with the physical laws. Is it an illusion?

A second serious problem associated with physicalism is the question of how the mind and how consciousness could emerge from non-mental and unconscious matter, that is, from interactions between elementary particles, atoms, or molecules. Or other way round asked: How to understand nature as something able to yield mind and consciousness?

My aim on this website is to address these two questions, the question of how the mind emerged from the physical world, and whether freedom is an illusion or not, given physicalism is true. A further problem of physicalism (but not only of physicalism) is „the hard problem of consciousness“. as David Chalmers called it. How and why do we have phenomenal experiences, see colors, feel pain, etc.?

I don’t know if we ever can explain this, since consciousness is the basis of all our explaining. The attempt to explain consciousness appears to me like the attempt to pull oneself by one’s own hairs out of a swamp (a German idiom; here, the swamp may be that of ignorance).

But I’m optimistic that answering the question of the mind’s emergence in nature and the question of freedom within determinism will help us to better understand at least some aspects of consciousness, for example, its function – such that it becomes clear why ourselves are not philosophical zombies [2], and why we can be quite sure that other people and higher organized animals as well have consciousness.


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  1. Peter Bieri. Analytische Philosophie des Geistes, Bodenheim: Athenäum Hain Hanstein 1993 (2nd Ed.) pp. 9ff.  [⇑]
  2. In an gedankenexperiment, David Chalmers has held the view that philosophical zombies are conceivable: beings which cannot be distinguished from humans in terms of physiology and behavior, but which have no phenomenal experience. See Chalmers, D. (1996): The Conscious Mind. New York: Oxford University Press.  [⇑]