Must All Facts Be Publicly Observable?

This was the view of the logical positivists of the early twentieth century. The facts exist, and all values are purely matters of emotional response to them, of personal feelings of pleasure or pain, without objective significance. But logical positivism collapsed because it was such a very peculiar theory. For a start, what exactly were the facts for positivists? They were what David Hume had earlier called "sense impressions," and what the positivists called "sense data." But if these were the facts, did they exist when not being observed in an objective physical world? Apparently not. Colors, tastes, and smells, as they appear to us, do not even exist in the physical world. They are momentary phenomena. They appear, and then they are gone—though, luckily, we also have memory impressions, which are mostly very imperfect copies of what they were like.

So what is the physical world? Probably the best-known British positivist, A. J. Ayer, said that the physical world is a logical construct out of sensory data. We do not have direct access to the physical world. It is a sort of postulate, for correlating all our sensory data and those of other people, too, in ways we can understand. But what about those other people? Do they exist in the physical world? They can hardly exist in a purely logical construct. What we are left with is just sets of different sensory data. We have to postulate that other sets than our own actually exist, as well as postulating that a physical world exists. But we can never actually verify that either other minds or the physical world exists. We postulate them in order to make sense of our experience.

Perhaps we need not worry too much about the problems of positivism since it is extinct. But it is salutary to remember that, in the 1930s and for quite a few years, many people, including many professional philosophers, thought that it was the ultimate truth about what really exists. It is a salutary thought because, when we think we ourselves have found the ultimate truth about reality, we may do well to remember what happened to the positivists and ruefully confess that the same thing may well happen to us. We, and all our favorite ideas, may well become extinct— and sooner than we think.

There are two lessons to learn here. First, we must be duly cautious about making claims to ultimate truth—that is equally true for religious believers and for nonbelievers alike. Since almost everyone else has been wrong so far, we should not be too confident that we are right. Second, it is not possible to escape disagreement. People see the world very differently because they put different personal interpretations on it. Even when we agree that all knowledge begins with experience, we cannot agree on what exactly experience is. For the positivists, it was value-neutral sensory and memory impressions. For existentialist philosophers and phenomenologists, experience, before we get to work interpreting and analyzing it, is a much more complex, fuzzy, holistic, and value-laden affair. Splitting it up into objective facts and subjective reactions is already an interpretation. For are objects not really beautiful, or elegant, or threatening? Do our feelings not reveal to us something about the character of reality? Do they not have a cognitive dimension?

Of course, the reality we perceive does not exist, as we perceive it, when we are not perceiving it. But, then, the allegedly neutral fact—the redness of a rose, for example—does not exist as we perceive it, either, when we are not perceiving it. Its redness, we may say, is contributed by the mind in response to the impact of an objective physical aspect of reality upon us. Why should its beauty not also be contributed by the mind in response to the impact upon us of a nonphysical aspect of objective reality?

Well, it may be said, because there are no nonphysical facts. Beauty is not objective. Well, neither is color. At least color is caused by objective physical properties. Now we approach the heart of the problem. Are all objective properties physical? Might there not be properties of beauty, of elegance, of intelligibility, and of goodness? If the idea sounds strange, it may be because we have been indoctrinated by the dogma that all facts must be physical and value-neutral. But what is the status of that dogma? Can it be verified? It cannot. It seems to be what the philosopher Alvin Plantinga (1983) calls a "basic" belief, one that is not founded on evidence or more basic axioms. How could you justify or refute an assertion that "all facts are physical and value-neutral"? Perhaps you could refute it by coming up with some facts that are not physical—like God, for instance, or facts about mathematical truths or about beauty and goodness or about the nonphysical contents of other minds. But every time you try to do that, you will probably be met with the reply that they are not really facts. The phrase for that tactic is winning by definition. Well, it may be said, to be a fact something must be observable. But beauty and elegance are observable, mathematical truths are discerned to be the case, and God has been apprehended, at least by Moses, Jesus, and Muhammad.

Ah, yes, but real facts must be publicly observable and agreed on by everybody. The irony is that it is doubtful whether even natural scientists would reach a consensus on that statement any longer. Superstrings, for example, are not publicly observable, probability waves for electrons are not publicly observable, and superposed particle quantum states are not publicly observable. Nor are these theories agreed on even by all competent scientists. There are major disputes about the objective reality of probability waves, about superstrings, and about how to interpret quantum events. So, even modern science no longer insists upon public observability and universal agreement as conditions for attributing actuality to things.

With logical positivism, the situation was even worse. Not only did positivists not require that all events must be publicly observable, but they actually denied that any events were publicly observable or that we could possibly observe any other minds that might be publicly observing anything. The much-cited "verification principle" was not a principle of public verification at all. It was a principle by which I could observe some state of affairs by having one or more sensory data (See Ayer 1936). Since I cannot ever have sensory data of what is going on in other minds, I cannot ever verify that other minds exist, and so I certainly cannot appeal to them to verify some state of affairs. It looks as if the requirement that all factual claims must be publicly observable, testable, and agreed on by all is looking rather shaky.

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