"but I am sure that the physical IS the mental."

This can be interpreted in three ways: the mental can be reduced to the physical (almost certainly what you mean), the physical can be reduced to the mental (this is sometimes called "idealism"), and bidirectionally, the physical and the mental interact with one another, interpenetrate one another, and cannot, in the end, be distinguished from one another as constituting discrete entities.

Let’s concentrate on physicalism, the view that there is nothing but the physical and that everything we describe as mental can, and ultimately should or must be described as physical, your mental states are really physical states, what we call “ideas” or “moral principles” are also just physical states or gibberish, words signifying, essentially, nothing. An implication of this kind of physicalism is that mathematical laws, such as the laws of arithmetic, must also be reducible to physical states. If these laws are “true,” then they are only true for human brains or for other physical structures that share much with human brains. But another view would be that the laws of arithmetic are true in any possible universe in which more than one thing exists, so presumably in any universe that is differentiated in any way. So the laws of arithmetic are either contingent, or they are not. If they are contingent, then they can be compatible with the view that they only apply for something like human brains, a certain kind of physical thing. But if they are not contingent, then they do not depend upon physical instantiation, hence not upon human brains or possible equivalents or analogs of human brains. And in this case, there is not just one kind of thing, the physical, but there are at least two kinds of things, physical things and things like mathematical laws.

These are considerations which lead me to ask, how can you be sure that the mental can be reduced to the physical and that there is really only one kind of thing, the physical kind of thing?

Dualism, the belief that mind and body are different, does not necessarily entail the belief that the mind survives the body. There was a presentation by a young man on http://mol.tv some years ago based upon a book he had written, that seemed to argue that every dualist must believe that “the soul” survives the death of the body, and I said that this was incorrect and insulting to dualists.

Let’s look at another implication of physical reductionism. Today, there are stories about two kinds of lawyers working in New York City. One kind of lawyer is willing to compromise with the Trump Administration and to promise to change their professional behavior as a result of threats to their interests qua lawyers being issued by the Trump Administration, and another kind is not. What is the ontological status of the legal and/or moral principles that lead one kind of lawyer to refuse this kind of compromise? Is the distinguishing behavior (the behavior presumably includes “beliefs” that motivate the behavior – again, entirely physical?) of this kind of lawyer based upon some difference in her brain and central nervous system, can it be traced back and attributed entirely to physical things, or does adherence to a legal and/or moral calling, to the idea of rule of law, for example, require the existence of something that cannot be reduced to the physical realm but which nevertheless influences human behavior in an important way?

I am not denying that it will always be possible for the physical reductionist to issue a promissory note to the effect that at some future time the physical mechanisms that produce the behavior of the lawyer who refuses to bend to threats, explicit or implied, issued by the Trump Administration, will be revealed (and, as a kind of corollary promissory note, behavior will be shown to be entirely physical, and beliefs will be shown to be entirely physical), but, as I have also argued previously in these fora, a propos of a Kaufman-Pigliucci dv, and of another dv between Robert Wright and a theologian at Johns Hopkins, a dv that Kaufman found to be incoherent and worthless, I don’t find such promissory notes very convincing. In the same vein, I am very sceptical about maximalist claims for artificial intelligence, largely because of the famous Chinese Room argument of John Searle. And speaking of John Searle, he was a great believer that neuroscience would solve the mind-body problem in his lifetime – in favor of physical reductionism. He is no longer such a believer, but I don’t know the details of how, why, and to what extent he lost this belief.

Just another aside. http://Meaningoflife.tv was a great project with some flaws. But I happened to rediscover on my computer, under the rubric of mind-body problem, an audio version of a dv between John Horgan and Sabine Hossenfelder that I had classified as being about the mind-body problem. Sabine Hossenfelder is now a very successful science youtuber, and I like her a lot. I was just watching her wrip to shreds a bad attribution study about climate change having contributed to the recent Los Angeles wildfires. But I’ve been watching other stuff in which she is involved, she thinks that particle physics has reached a dead-end, essentially, and now involves a lot of pseudo-science that is motivated enirely by the financial interests of the scientists who do it. And Dave the Science guy, if that’s what he calls himself, has in turn condemned Hossenfelder on this particular point, he doesn’t think she’s stupid or incompetent, he just thinks she’s wrong and dangerous on this particular point. Hossenfelder was on bhtv with another physicist once, that was really good, and I think she did a dv with Robert Wright once.

By the way, Juan, ohreeally once said to me something to the effect of “In the end, we are all dualists.” In a similar vein, in the past year I heard Chomsky say in a recently recorded video that no one behaves, or could behave, as though he does not have free will. The clear implication of this remark was not that free will is an illusion, precisely the opposite. But physical reductionism implies that free will is an illusion, it’s impossible. However, a proponent of compatibilism and what must be a closely related theory, the theory of “levels of explanation” (micro-level explanations are not the same as macro-level explanations and should not be expected to follow the same laws), is in our midst.

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