(By "legitimization of belief" I mean clarification as to why I believe something and why I believe you should believe the same thing. So you and I have a way of cooperating in an effort to agree, by first agreeing upon what criterion or criteria we will use to legitimate belief.)

One could imagine a situation in which everyone on the planet actually agreed to a complete set of beliefs about the way the world is, was, and will be, that set of beliefs being maximally accurate. That situation will undoubtedly never arise, of course, but it is actually the goal that science works toward, namely, the increasing development of a set of models that are all consistent with one another and are maximally capable of yielding specific predictions that turn out to be, or would turn out to be, what actually happens in certain situations, including situations in which we have done certain things.

And here I would like to mention what I have come to refer to as the "second exponential change," making our species drastically different from all other species on this planet and drastically different from the way we were before this change occurred. (Actually, the change is still occurring, but it is quite easy to see, including the exponential nature of it.)

The first exponential change, remember, was the development of the essentially infinite ability to use symbols and the rules for using them, the most important example being language, consisting of words and the rules of syntax governing the construction of sentences. We do not know how far back we must go in the history of our species, or perhaps genus, before we can say that we had essentially no language (another example of drawing a line on a terrain), but it is apparent that there has been a drastic increase in the ability to use symbols somewhere along the way, with such a marked escalation in that capability that we might say that it is now essentially infinite, that is, that we now cannot easily imagine a limit.

The second exponential change began accelerating noticeably during the last two or three thousand years, and especially during the last two or three hundred years. It has consisted of the development of (first) the rules of logic and (more recently) the rules of evidence, which serve as the additional legitimization criteria for the accuracy of scientific models, or sets of agreed-upon beliefs, additional to the criterion simply of agreement regarding the specific beliefs, or propositions, or models. In other words, it is not enough just to agree. In addition, what we agree to must be consistent with (be able to be legitimated by) the rules of logic and the rules of evidence. These rules of logic and rules of evidence have also, themselves, been arrived at by agreement (because of our seeing how well they work to produce beliefs that yield accurate predictions and that therefore enable us to avoid mistakes).

The rules of logic provide a way of ascertaining whether a set of propositions (linguistic, mathematical, etc.) are internally consistent (non-contradictory). If we are constructing a model of something and there is a part of it that can either be one way or the opposite, then we lose the ability to predict the relationships in the thing that is being modeled. If part of the model can be one way, but also doesn't have to be, then of what use is that part of the model (unless of course that is true of the thing being modeled)? And so if we are linguistically modeling a set of beliefs and we arrive at two sentences that say the opposite thing (are contradictory according to the rules of logic), then of what use is that set of beliefs?

The rules of evidence are those rules governing the obtaining of and management of (e.g., analysis of) data from natural observations or contrived experiments that determine how confident we should feel about our conclusions (beliefs, or models) arrived at from that data (conclusions about the way the world is, was, or will be). The basic idea is that we say, "According to theory X, if we do Y, we will observe Z, whereas if we don't do Y we won't observe Z," and then if we actually do Y, and we actually observe Z, and especially if we also don't do Y and don't observe Z, the confidence in theory X is increased. If we don't get such results, something is probably wrong with theory X, or perhaps with some other theory that has already been accepted and is also relevant to whether Z will be produced or not. (In this paragraph, I am using "theory" generally to mean any proposition.) The rules of evidence are tools used to avoid making mistakes by, for instance, misinterpreting coincidence as causation or failing to see alternative explanations for findings.

So just as the Subjective Model is an ever-evolving model within an individual (of course containing components that will be modified as time goes on), in the same manner the Objective Model is an ever-evolving set of models "within our species," and within each member of our species, those models gradually becoming increasingly internally consistent and increasingly accurate (and therefore more useful) with the passage of time, this consistency and accuracy being promoted by the rules of logic and the rules of evidence, respectively. And it is the commitment to promoting (in self and in others) the development of beliefs and belief systems which, when modeled linguistically, can be shown to meet the criteria of the rules of logic and the rules of evidence, or shown to be logically consistent with other beliefs shown to meet these criteria, that I will refer to as "rationality" in this presentation.

Notice that the Subjective Model is communicated very often by poetry and art (in which, for example, the connotations of words add meaning to the impressions conveyed), whereas the Objective Model is communicated very often by technical literature that involves well-defined technical terms and symbolic systems such as mathematics, chemical equations, statistical computations, physical diagrams, etc. ("Communicated" here means modeled linguistically or otherwise symbolically, and thereby shared with others.)

Notice also that the response to presentations of a subjective model, through literature, poetry, art, etc., is expected to be of the nature, "Well, what this means to me is…," whereas the response to presentations of an objective model, usually through scientific literature, is expected to be "Well, what this means is…." So within scientific literature there is an important reliance upon precise definitions of terms. The more important that agreement becomes, the more important precision of definition of terms becomes. (This assertion can be seen to be true in legal matters, also.)

Now let us be clear that whereas the "Objective Model" is represented in its extreme by the scientific belief systems (that many individuals have no access to or awareness of), it also exists in its more general form in the "knowledge" (set of beliefs) that is generally held by most all within that culture or subculture, and communicated in much less precise and accurate ways (with much use of metaphor). But even within a culture or subculture that is not well educated with regard to the sciences, there still is some valuing of rules of logic and rules of evidence, or rationality, such that an individual may be considered "irrational" if he or she expresses beliefs that are seen as illogical (self-contradictory) or unfounded (not supported by some sort of evidence). So we value the rules of logic and the rules of evidence to a certain extent, even without having a strongly scientific orientation and even without any clear understanding of what those rules, as used by scientists and academicians, actually are.