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.
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.