Many of us presume that something in the physical world may cause something in the mental world to happen, and vice versa. Presumably we can demonstrate that we sometimes can predict that something will happen in the mental world if we know that something has just happened in the physical world (e.g., brain stimulation causing alterations of conscious experience), or vice versa (e.g., one's decision or intention to move one's hand causing one's hand to move).

But if entities in the mental world cause things to happen in the physical world, why are those mental entities not represented by variables in the equations that are used to model the interactions in the physical world? Why do we not find, for instance, that the events observed in particle accelerators are influenced by the thoughts, feelings, and wishes of those standing around watching the results of such experiments? Why do we not find that the emotions of the chemist affect the chemical reactions being brought about? If they do, why would we not find equations like "hydrogen + chlorine + anger -> hydrogen chloride + nostalgia"?

Now I realize that many people believe that such influences do occur. Phenomena such as levitation and other kinds of magic involve the mind directly influencing the physical world, in ways not predictable by the known rules of the universe ("natural laws"), but only by the wish and/or intention of the individual engaged in the magic, perhaps accompanied by some sort of ritual behavior (e.g., waving of a wand). But I wish to call attention to the lack of verification of such interactions by scientists who are respected by peers who review their fellow scientists' work and attempt to replicate and/or challenge their findings.

It is, of course, widely recognized that mental phenomena in the experimenter, such as wishes for specific outcomes, may affect the outcome of observations and experiments. However, the usual explanations for that kind of influence (experimental bias) have to do with erroneous setups of experimental situations, or errors in observation or statistical analysis. They do not have to do with a presumed direct effect of the mental state (e.g., "wish") of the experimenter on the studied operation of the rules of the universe. The experimenter's (mental) wish indeed does affect his or her (physical) behavior, how he or she performs the experiment. But this experimental bias is not an example of the mental world directly affecting the functioning of the physical world beyond the behavior of the experimenter. Thus, the feelings of the experimenter do not end up as variables in the equations describing the functioning of the part of the physical world that is being studied.

But of course this situation indeed is an example of the mental state (e.g., wish) of the experimenter presumably affecting the physical activity of the experimenter, that is, his or her behavior in the physical world.

So there still remains the observation that feelings, beliefs, motivations, etc., namely, mental phenomena, seem to cause things to happen in the physical world, as, for example, when a decision in my mind to move my hand is predictably followed by movement of my hand, or when my becoming afraid of what I am seeing is predictably followed by an increase of adrenalin in my bloodstream. Are these indeed clear examples as to how the mind can affect the body, i.e., how mental entities and processes can cause things within the physical world to happen? And, again, if this is so, why do these mental entities never show up in the explanatory formulae or equations describing how things work in the physical world? Why are these things absent in what is studied by the physicist, the chemist, the biologist, the neurologist, the astronomer, etc.?

Another related dilemma is created if we ask the question as to where the interaction between the mental world and physical world takes place. People are used to the idea that it is not possible to find mental entities somewhere in the physical world, but if there is indeed an effect of mental entities on some part of the physical world, then the location of that effect, the place in the physical world where it is presumably happening, surely could be identified. At one time, some people apparently thought that this location was in the pineal gland in the center of the brain, but no one believes that now, as far as I know. The question just remains unanswered. And we may ask why it remains unanswered. If we were to determine where the physical world is influenced by a mental entity, then we should be able to see an example of something happening at that place in the physical world that seemed contrary to what would be predicted by the rules of the universe ("natural laws") that describe only interactions among physical entities. Something "strange" should be observable at that location.

So on the one hand most people believe there is a causative interaction between the mental world and the physical world, but on the other hand no one has ever been able to locate, much less explain, that interaction. This fact raises the possibility (or probability) that the question itself may be flawed, that the question itself may contain assumptions that should not be made because of not being possible or because of not being clear and unambiguous. But of course we can't just assume that.

So now we come to a solution to the "mind-body problem" that is sometimes offered, which feels like it is on the right track, but still has some puzzling aspects to it. That solution is that when a mental event and a physical event always take place at the same time, it may be that neither is causing the other, but that those are just two different "aspects" of reality, or of what is happening in reality. If this is true, then it would not be appropriate to speak of a "physical world" as distinct from a "mental world." It would not be appropriate to speak of "physical entities" and "mental entities," but instead perhaps to speak of physical "aspects" and mental "aspects" of entities. But if that is what is happening, how come there are these two "aspects" of reality, or of the world? What is the reason for there being two aspects of reality rather than just one? And what does it mean to say that reality has two (or more) "aspects." And why do some things (e.g., people) have two aspects and others (e.g., rocks) just one? Indeed, I think that we are getting on the right track with this explanation, but that there needs to be quite a bit of additional explanation, and when we are finished, I think some important and influential conclusions can be drawn. But this remains to be seen.