Since the Physical Model is so well recognized and understood, at least from a distance, we will not need to focus on it specifically. The Mental Model, however, is a little more obscure, despite being in widespread use. It is that set of models that are built upon primary mental entities, and, similar to the Physical Model, have been elaborated on extensively through the addition of secondary mental entities.

We are saying that feelings, thoughts, perceptions, etc., in other words all "primary mental entities," are components of subjective experience. But as a part of the Physical Model component of the Objective Model, the most thoroughly appropriate way of referring to them ("feelings, thoughts, perceptions," etc.) is "whatever it is that is going on in the brain of the individual when he or she reports having particular subjective experiences (assuming of course that his or her report is accurate)."

But that is not how we are limited in our linguistic modeling.

Obviously, such linguistic modeling as the above ("whatever it is…") is somewhat awkward and cumbersome, so it is not surprising if we attempt to simplify our linguistic behavior by letting fewer words mean what we are trying to say. So instead of saying "whatever it is that is going on in the brain of the individual when he or she reports having particular subjective experiences," we simply say "what he or she subjectively experiences." And we can omit the observation and study of the neuronal connections and just look at the correlation of his or her reports of "what he or she experiences" with what that experience is "of," the thing in the Physical Model that that experience is a model of. This is a linguistic convenience. But you can see that this linguistic simplification is the introduction, so to speak, of the Mental Model, as a simpler model to use, under some circumstances, than the Physical Model. In the Mental Model, we simply leave out reference to what is going on in the brain.

Also, the "whatever it is that is going on in the brain" when a person is reacting to a situation is extremely complex, so if we are trying to study a person's reactions to situations, we will have a much easier time using his or her reports of subjective experience rather than having to look everywhere in his or her brain to see what is happening. This is no different from speaking of how one nation reacts to the "behavior" of another nation. It is far easier to say that one nation feels threatened by another nation than to try to describe all the reactions of every person in that nation, even though that "nation" exists by definition only. And the same is true of pressure systems in talking about the weather (as opposed to talking about molecules) and recession in talking about the economy (as opposed to talking about dollar bills and coins and ledgers).

So indeed we have two different models, the Physical and Mental Models, to deal with what is really only one thing, and sometimes one of those models works best and sometimes the other does. More specifically, that "one thing" is the reaction of the animal, or its brain, to things within its environment, as through perception. We can study processes such as neural processes, reflexes, instinctual behaviors, and conditioning (learning) using our models of the neurons, etc., in the brain or nervous system (using the Physical Model). And we can study processes such as breakdown of relationships using models of the feelings and thoughts of individuals (using the Mental Model), without paying any attention to neurophysiology. As noted, this is little different than choosing to study pressure systems for prediction of weather, rather than atomic and molecular kinetic interactions.

So what has happened is that for a number of reasons we have attempted to develop a model that we can all agree upon, of the set of subjective experiences of individuals, thus making that model a part of the Objective Model. In other words, we wish to arrive at agreed-upon beliefs about (or an objective model of) everyone's subjective experiences, such that the model would even account for the presumed differences between individuals' subjective experiences (e.g., perceptions), and also their predictable interactions. Examples of the use of such models would be studies of "how memory functions" or "the meaning of dreams" or "the nature of optical illusions," or "the relationship of beliefs to feelings," or "the reliving of experiences," or "the relationship of obsessions to compulsions," etc. The data we would have to accept would be individuals' reports as to their subjective experiences, with, of course, the recognition that those reports might not be accurate. (Later, some might say, "I was mistaken," or "I meant something different," or "I lied," or "I didn't understand the question," or "That's the way it seemed to me," etc.) The subjective experiences being studied would not themselves be observed; only the reports of them would be (or perhaps behaviors, other than reports, that were assumed to be associated with those subjective experiences).

Note again that the "material" used for this modeling, as always, comes from subjective experience. This is the only material available, as discussed earlier. So when, in the Mental Model, reference is made to a feeling or a thought, one uses one's own experience that has been labeled that way as such material. This is in one respect no different from using billiard balls as material to model atoms. Atoms cannot be observed, but they are (somewhat) like billiard balls that I have experienced. Subjective experience of others cannot be observed, but it is assumed to be like what I experience. You and I use entities within our own subjective experience to model that which cannot be observed.

But there will need to be important clarification regarding a linguistic ambiguity in order to maintain a consistent lexicon, or way of using words.

We can both of us look at (and point to) a house and start talking about the house. But there is a drastic change of subject when we start talking about your perception of the house and my perception of the house (or "perception" itself). When you see the house, what you are seeing is the house, not the seeing of the house. Your subjective experience is of the house, not of the subjective experience of the house. When we start talking about "the perception of a house," or "the perception (of anything)," we are sometimes beginning to talk about the unseen (by anyone). The house is seen; the perception of the house is unseen.

So "perception" itself is really a secondary mental entity, not a primary mental entity. No one sees a "perception." An awareness of this ambiguity can be strengthened by contrasting two common uses of the word "perception," namely as in "your perception of the house" and "your perception of the house." Or even more, one can contrast "your perception of the house rather than the barn" and "your perception of the house rather than your memory of the house." Note then that "perception of the house" can have two different meanings, referring either to a primary mental entity or a secondary mental entity. Here is another example of words having different meanings in different contexts, but such that people will not easily recognize the difference in usage, or meaning.

Another way of intensifying awareness of this difference is to consider what is meant by the word "pain" in (1) a request put to an injured person to describe where the pain is being experienced, and in (2) a statement about the inability of people with certain injuries of the spinal cord to experience pain, or the role of pain in the motivation for attainment of physical fitness. The primary mental entity is a specific experience experienced by one specific person, though we can empathize with that person and imagine the experience. When we are talking about "experience of that sort," we are talking about a secondary mental entity, because there is nothing that we are referring to, and meaning, that is, was, will, or could be experienced by one person and one person only. Your pain in your right knee can be experienced only by you. Perception of pain is something that we all have equal access to, in that none of us experience it but we regard it as an entity that we can talk about and develop further beliefs about. This is like the difference between talking about three individuals (each having a name) versus the group (that could also have a name) consisting of those three individuals, producing a set of four entities, the last one created by definition only. "Perception of pain" is an entity created by definition only, added to our growing set of secondary mental entities.

We have already considered "subjective experience," meaning all the things you experience, that no one else can experience (because it is your own subjective experience), and also the Subjective Model, meaning not only your own subjective experience but also all of your own beliefs about your own subjective experience, what you have come to expect (predict), acquired primarily from your own previous subjective experience alone (that is, independent of language and independent of having been "told" by others).

But when talking about the Mental Model, we are now talking about a sub-Model within the Objective Model, so we are talking about things that we can all, at least potentially, agree upon. And as we increasingly develop the Mental Model (similarly to our continuous development of the Physical Model), what we are all agreeing upon, or trying to agree upon, is beliefs about subjective experience "in general," that is, not just your subjective experience at a specific point in time or a specific period of time, but anyone's subjective experience, or subjective experience itself, a secondary mental entity. We are attempting to find the rules by which the entities "within" subjective experience interact, so that we can use that modeling to predict and thus to "understand" (have accurate beliefs about) each other better.

For instance, we may not be talking about your sadness that you are feeling right now (if you are), but about sadness, as it is felt by people under certain circumstances, and what its effects are. Just as we could write an article about entities such as houses, or sunlight, or atoms, or black holes, we could write an article about entities such as sadness, or fear, or thinking, or imagination, or the experience of pain. Such an article would be substantially different from, for instance, a fictional, biographical, or autobiographical account of an individual's interesting, exciting, joyous, depressing, irritating, and anxious experiences, the account being linguistic modeling using many primary mental entities, with of course probably some additional secondary mental entities.

So we are talking about our using of the Mental Model, and our trying to arrive at beliefs in it that we can all agree upon. So that agreement is the first step (after the agreement in the use of symbols and syntax, that is, language) in the building of the Objective Model, in this case the Mental Model, a sub-model of the Objective Model.

Okay, so since the Objective Model is (first of all) based upon agreement, what is it that is being agreed to in the Mental Model, a sub-model of that Objective Model? If the entities in the Mental Model are ones that cannot be pointed to and experienced by everyone, and therefore measured, then what is the basis of any agreement within the Mental Model?

Remember that in the Subjective Model we have the situation in which you have come to believe (as a part of your Subjective Model) that things, as you perceive them (as they are within your subjective experience), continue to exist without change even when you are no longer perceiving them and thus independently of your experiencing them. The road continues as imagined around the curve, and the experience of going around the curve confirms that. This assumption allows you to agree with others that certain objects exist, and have certain characteristics, or properties, that you can linguistically model (talk about), that are not dependent upon your experiencing them, perhaps even ever. This assumption is one that others are making, also, so with your and their linguistic modeling (discussion, etc.), you can come to agreement about things that are not within your subjective experience (and may never be). Thus, even though "objective modeling" (development of the Objective Model) begins with the equivalent of "pointing," as language is being learned by the small child, "pointing" is ultimately unnecessary in the process of arriving at agreement. If others are making the same sentences as you would make, that is enough for agreement to be considered achieved (with of course the uncertainty produced by the possibility of misunderstanding and untruthfulness). And that process of continuing to work toward agreement is the continuing development of the Objective Model.

Agreement can occur in the Physical Model because you and others are using the same sentences as you describe what you and/or they believe. Initially, the act of pointing was indeed necessary, but as time went on, you and others began talking about things that neither you nor they could experience and therefore point to. This would be true, e.g., of atoms, and things in the past, and things on the other side of the earth, and of course eventually "warped space-time," etc.

But we recognize that primary mental entities are ones that are not experienced by anyone but you (or some other person and not you). So we are talking again about unseen (un-experienced) entities. We are talking about entities that presumably exist "in" other people, entities that you can't "see." (The use of the word "in" will be discussed later.) But it will turn out that you and others can agree with regard to them (by agreeing to the same sentences), thus making possible the continuing development of the Objective Model, and, more specifically, the Mental Model.

But what if we are indeed all talking about the pain that a certain specific person felt when she fell down?

We can all talk about "such pain," that a person would experience upon falling down. We all have the same access to that "pain-in-general," namely, no access. None of us can experience it, but we all can talk about it. It is a secondary mental entity, just as an atom or the atmosphere is a secondary physical entity.

Yes, you say, but what about her? She is indeed experiencing the pain. And she is talking about it. So one person actually is experiencing it, among all those talking about it. What she is modeling with her language is her own subjective experience of pain and her own Subjective Model beliefs about that pain. So, does that mean that she, the one experiencing the pain, cannot use the Mental Model regarding her pain (because she can experience it, and in fact is experiencing it), and has therefore to be left out of the conversation? No, of course not. This is an example of the fact that we all are using our Subjective Model all the time, even if we also are often using the Objective Model at the same time.

So at the same time that she is experiencing her pain and developing beliefs about what makes it less and more (e.g., what positions she can get in), and is linguistically modeling her subjective experience of her pain for us (telling us where she is experiencing it and what it feels "like") and also linguistically modeling her subjective modeling of that pain (for instance, what she has come to believe from her experience makes it worse or better), she can also be talking with us about what she believes to be the causes of pain like that which she is experiencing and what usually helps people who have such pain (such as general attitudes toward pain), and we can offer our own opinions about that, all of this discussion making use of the Mental Model, and secondary mental entities in that Model.

(Remember that the brain can do more than one thing at the same time, like remembering what happened yesterday while tying one's shoelaces, or answering a person's question while wondering why he or she was asking it and thinking about what question to ask in return. So many models can be active in the same brain at the same time.)

So, what is the difference between our talking about primary mental entities and our talking about secondary mental entities?

How can you and I talk about primary mental entities? The answer is that I can talk about this pain that I am experiencing, or experienced yesterday. I can also talk about whatever it is that you are experiencing or have experienced that you are calling pain.

And how can you and I talk about secondary mental entities? The answer is that we can both talk about pain in general, what seems to cause it, what can be done about it, etc.

So perhaps you can see that as I talk about my pain that I am experiencing, I am linguistically modeling what I am experiencing within my own subjective experience, including my beliefs that are a part of my Subjective Model. As you hear me linguistically modeling those beliefs, you are developing beliefs within your own Objective Model, beliefs about what I am subjectively experiencing. As you make the assumption that I exist and have subjective experience and am linguistically modeling that subjective experience for you, you are developing your own Objective Model, one in which I have an invisible, opaque balloon-like container within which I am experiencing certain primary mental entities, one of which is the pain I am talking about. And if we are talking about the specific pain that I am experiencing, i.e., the way I am experiencing it, we are talking about a primary mental entity, talking about it from two positions, yours and mine. But as we talk about pain, and causes of pain, we are talking about a secondary mental entity, "pain." We are talking not about what you or I are experiencing, but how the world works.

Remember that, yes, subjective experience consists of primary mental entities, but only when using the Objective Model. The Subjective Model has no use for entities called "primary mental entities." This whole discussion is a development of the Objective Model.

(Note that what we are talking about when talking about a secondary mental entity is most often referred to using the concept of "abstraction." People refer to "this pain" and "that pain," and then, "abstractly," to "pain in general." This concept of "abstraction" (or generalization) is frequently highly useful, but for our purposes the use of the term would obscure with a label the very thing that we are trying to talk about in greater depth. The reason is that "abstraction" refers to a linguistic process, one that brings new words into existence in response to the experience of "similarity" or "familiarity." What we are talking about in this presentation is in part that experience of "similarity" or "familiarity" itself, understanding it in terms of the modeling concept. So the concept of "abstraction" will not be an important one in the modeling involved in this presentation, which is trying to clarify phenomena underlying, in part, what we refer to as "abstraction.")

Regarding the person who was telling us about her pain, we can imagine that there are two different neuronal networks (probably having a fair number of neurons in common) active in her brain, one as she linguistically models for us a part of her Subjective Model of her subjective experience (telling us about her pain) and the other as she linguistically joins our conversation, using the Objective Model, about the kind of pain she must be experiencing and, for instance, what we humans think can be done about pain like that, and what part of the nervous system must be active for that experience of pain to be occurring. And it is possible to talk about pain, as a secondary mental entity, without calling up within the imagination the memory of what pain feels like, whereas if we are talking about a person's specific experience of a specific pain, we tend to use empathy and "imagine what it must be like," that imagination being a model of (belief about) what is happening.

So, again, the primary entities in the "physical world" are ones that we all have equal access to, whereas the primary entities in the "mental world" are ones that are accessible to no one other than one person, even though we can all talk about them and attempt to come to agreement about them, using explanatory secondary mental entities, such as "pain," "thought," "imagination," "intention," "abstraction," "intuition," "will power," "grief," etc.

But now if the primary entities in the mental world cannot be observed by more than one person, and thus none of them can be pointed to, how can we have agreement about them, beyond just blindly taking each other's word for beliefs about them? And what is the role of measurement in such agreement?

What all of us can indeed observe when a person reports having some particular subjective experience are certain things in the "physical world" that we model within the Physical Model (the primary entities of which we all have access to), and that we have come to associate with reports of things within the "mental world." We have come to associate, for instance, certain changes in the observable body, such as a reddened face, with a report, such as that of a feeling of embarrassment. And we can observe certain behavior that looks to us like "flight" or "avoidance," as well as certain results of measurements indicating hormonal changes and neurological processes, when a person reports a feeling of fear. And when your vision is tested, by having you report what you are seeing, the ophthalmologist is associating those reports with things about your body, that is, your eyes and the nerve pathways in the nervous system that are involved, consisting of primary and secondary physical entities.

And of course note that a "report" is itself a primary entity in the physical world. It is something we can all point to and experience.

(It may be subjectively experienced differently by different people, including the one reporting, this being a difference in perspective, but there can easily be agreement as to whether the report is "there" and what the report is. "So you are saying X?" "Yes, that is indeed what I am saying." We can all point to the report and agree as to what it is. We can agree that when we point to the report, we are pointing to the same thing.)

This "equal access" to reports and other events and situations in the physical world that are believed to be "correlated" with mental entities and situations in the mental world is what allows for agreement that goes (a little) beyond simply taking another's word for it. So it is because we can correlate primary entities in the physical world, such as facial expressions, changes in skin color, lab results, and results of imaging techniques, with reports in the physical world of primary mental entities that we can come to agreement about the "existence" and "properties" of mental entities. It is this correlation of (1) reports (which are entities in the physical world) of entities or situations in the mental world with (2) other entities or situations in the physical world that allows us to use the scientific methods (rules of logic and rules of evidence applied to measurements) with regard to mental entities and situations. Thus, psychology can become a science.

A belief that there is a "correlation" is a belief that there is predictability of measurements of one thing given the measurements of something else, and a belief as to how to arrive at such predictions (usually the mathematical equation to use). We have learned that we can predict certain reports of subjective experience given certain observations, even measurements, of certain things about behavior or the activity of neurons in the nervous system or the concentrations of certain substances in the bloodstream, and vice versa.

(And, by the way, the field of psychology attempted to deal with this concern about the inaccessibility of mental entities by focusing attention only on the physical entities that are presumed to be related to mental entities, thus developing the sub-field of "behaviorism." And in the area of public "mental health," those who fund the procedures to be of help developed concerns about what they were paying for and started using the term "behavioral health," subtly moving away from the concern about and empathy for suffering, and replacing it with what could be measured. The extreme of this has been to establish goals regarding the reports of patients by specific target dates, etc. "The patient will make 75% fewer threats of suicide by target date xx/xx/xxxx." You may detect that I have difficulty following this trend, and indeed I have noticed a more recent lessening of the trend, though the term "behavioral health" is still quite prevalent, and probably more a hindrance than a help in the effort to alleviate suffering.)

One additional point, mentioned earlier, to emphasize, which might at first seem surprising, is that no measurement is possible of mental entities. Remember that measurement requires that two or more people can make the same observation and experience the same result, that is, be able to point to the same thing and agree to what it is. But mental entities cannot be observed by two or more people. Yet, for psychology to be a science, and for other reasons also, there is a need to be able to measure, and thus to point. So how is this done?

An assumption is made that the existence of a mental entity or a mental process can be reported by an individual such that the observation of the report can be used in the place of the observation of the mental entity or process, for the purpose of measurement. And this is true not just of observation of reports, but also of observations (also in the "physical world") of other behaviors and of various physical, chemical, and imaging results, all considered to be adequately reliable and valid substitutes for (models of) the mental entities and processes of concern. This assumption, that is, belief accepted without legitimization, is of course a model.

The Mental Model has within it many different models, that most people eventually become at least somewhat acquainted with.

Sigmund Freud developed a model that consisted of the Conscious, Preconscious, Unconscious, and Reality, changing it later to a model that consisted of Ego, Superego, Id, and Reality. A "hydraulic" model of mental functioning has been in great use, consisting of the idea that certain "feelings" or "drives" build up "pressure" and tend to "come out" in various ways, thus relieving that pressure "inside." There have been many, many models constructed, usually presented accompanied by diagrams that make the models analogous to models of the physical, spatial world, such that there are boundaries and areas in which entities reside, with perhaps interactions among entities in neighboring areas. When someone presents his or her new ideas to groups of people, he or she often uses such diagrams on, for instance, a screen.

So in these mental models (that the Mental Model consists of), primary mental entities interact with one another according to rules inherent in the modeled rules of interactions between secondary mental entities. The Ego behaves in certain ways, having certain functions that are mechanisms (properties involving action) that result in varying degrees of success in achieving certain goals. So a specific example of some mental event, involving one or more primary mental entities, is just an example of how such things occur among certain secondary mental entities. "His ego used repression to keep his anger confined to his unconscious, because of pressure from his superego, that has a strong tendency to produce guilt in response to perceived internal anger and especially to any expression of it." Of course none of that sentence contains any primary physical entity to which we can all point such that we can agree that we are pointing to the same thing. Nevertheless we can all agree if we find ourselves using the same sentences, containing the same agreed-upon meanings of the words in them.

As the physical sciences have made such progress, demonstrating amazing abilities to do things, the mental sciences have tended to be less respected and admired, and even more suspected of inaccuracy, because there has not been anything like such demonstrable progress in the ability to do things. And those involved in some study of or application of the various mental models have often wished to try to obtain a higher status of recognition and greater degree of usefulness by developing ways of utilizing the Physical Model (e.g., information from the physical sciences) such as to be able to engage in actual measurement. These measurements, considered to be of entities that are "correlates" of mental entities, are as we have noted, obtained with things like psychological tests and questionnaires the results of which can be "quantified" (utilizing numbers) and with various tests of entities in the nervous system or body in general. But although those test results can be correlated with other things in the physical world, there can be no actual correlation with mental entities, which cannot be measured (or even pointed to).