There is no possible universe in which dualism holds due to the interaction problem
Hopefully making this point won’t derail your discussion:
Quantum mechanics is not deterministic. This is a gap which dualists can use. The major names here might be John Eccles (in neuroscience) and Henry Stapp (in physics).
If a theory says that something is fundamentally random—e.g. when a nucleus undergoes radioactive decay—then the event had no cause. It just happened. This is an opportunity to extend the theory by introducing a cause. In these dualistic quantum mind theories, a nonphysical mind is added to quantum mechanics as an additional causal factor that determines some of the randomness.
This is an opportunity to extend the theory by introducing a cause. In these dualistic quantum mind theories, a nonphysical mind is added to quantum mechanics as an additional causal factor that determines some of the randomness.
Firstly, how would we know that the correct way to extend the theory was to introduce a nonphysical mind as a cause? How would we tell the difference between the validity of this hypothesis and that of the infinite other possible causes?
Secondly, what is the difference between something physical and nonphysical? I hope I can assume that you agree that if something exists, then it behaves in some way. It is then up to us to try to describe that behavior as far as we can. Whether or not something is physical or not seems meaningless at this point. Quarks might as well be considered supernatural, magical, nonphysical objects whose behavior we happen to be able to describe, including how our mundane, physical reality emerges from it.
Supernatural, magical and nonphysical are contradictions in terms unless one decides on some arbitrary distinction between behaviors that are such and those that are not, because they will regardless behave in some way and we can predict that behavior inasfar as we can describe it.
what is the difference between something physical and nonphysical?
In naive, pre-scientific, pre-philosophical experience, there’s a world of things that we know through the senses, and a world of our own thoughts and feelings that we know in some other way. That is the root of physical versus non-physical, or matter versus mind.
Once science and philosophy get involved, the dividing line between physical and nonphysical can shift away from its naive starting point. Idealist philosophy can try to claim everything for the mind, physical science can try to claim everything for matter.
In the case of these quantum mind theories which have a Cartesian kind of dualism (mind and matter as distinct kinds of “substance”), there is no attempt to assimilate the mental world of thoughts and feelings, to the material world of things.
For example, in the Eccles theory, apparently thoughts and feelings in some way set the probabilities of quantum events in the synapse, and that’s how the interaction of substances occurs. Thoughts and feelings may fairly be called non-physical in such a theory, because there is no attempt to identify them with attributes of the physical brain. The mental realm is made of thoughts and feelings, the physical realm is made of particles with mass and spin, they are separate kinds of entity that interact in a specific way, and that’s it.
How would we tell the difference between the validity of this hypothesis and that of the infinite other possible causes?
Any theory (whether dualist, monist, or something else) that includes both mind and matter, is constrained by two kinds of data: introspective observation of thoughts and feelings, and physical observation of the material world. So you test it against the facts, like any other theory. Facts are not always easy to ascertain, they may be ambiguous, disputed, or denied, but they are still the touchstone of truth.
Hopefully making this point won’t derail your discussion:
Quantum mechanics is not deterministic. This is a gap which dualists can use. The major names here might be John Eccles (in neuroscience) and Henry Stapp (in physics).
MWI is deterministic.
How could dualists use a random process?
If a theory says that something is fundamentally random—e.g. when a nucleus undergoes radioactive decay—then the event had no cause. It just happened. This is an opportunity to extend the theory by introducing a cause. In these dualistic quantum mind theories, a nonphysical mind is added to quantum mechanics as an additional causal factor that determines some of the randomness.
Firstly, how would we know that the correct way to extend the theory was to introduce a nonphysical mind as a cause? How would we tell the difference between the validity of this hypothesis and that of the infinite other possible causes?
Secondly, what is the difference between something physical and nonphysical? I hope I can assume that you agree that if something exists, then it behaves in some way. It is then up to us to try to describe that behavior as far as we can. Whether or not something is physical or not seems meaningless at this point. Quarks might as well be considered supernatural, magical, nonphysical objects whose behavior we happen to be able to describe, including how our mundane, physical reality emerges from it.
Supernatural, magical and nonphysical are contradictions in terms unless one decides on some arbitrary distinction between behaviors that are such and those that are not, because they will regardless behave in some way and we can predict that behavior inasfar as we can describe it.
In naive, pre-scientific, pre-philosophical experience, there’s a world of things that we know through the senses, and a world of our own thoughts and feelings that we know in some other way. That is the root of physical versus non-physical, or matter versus mind.
Once science and philosophy get involved, the dividing line between physical and nonphysical can shift away from its naive starting point. Idealist philosophy can try to claim everything for the mind, physical science can try to claim everything for matter.
In the case of these quantum mind theories which have a Cartesian kind of dualism (mind and matter as distinct kinds of “substance”), there is no attempt to assimilate the mental world of thoughts and feelings, to the material world of things.
For example, in the Eccles theory, apparently thoughts and feelings in some way set the probabilities of quantum events in the synapse, and that’s how the interaction of substances occurs. Thoughts and feelings may fairly be called non-physical in such a theory, because there is no attempt to identify them with attributes of the physical brain. The mental realm is made of thoughts and feelings, the physical realm is made of particles with mass and spin, they are separate kinds of entity that interact in a specific way, and that’s it.
Any theory (whether dualist, monist, or something else) that includes both mind and matter, is constrained by two kinds of data: introspective observation of thoughts and feelings, and physical observation of the material world. So you test it against the facts, like any other theory. Facts are not always easy to ascertain, they may be ambiguous, disputed, or denied, but they are still the touchstone of truth.