In science, observation serves as a starting point and as a testing ground. That which is spoken of in science, however, need not be observed or observable. Consider an atom, a common subject of scientific investigation, considered by some to be as real an object as a table. To verify the existence of a table well enough to convince most anyone is as easy as seeing and touching it. The reality of that which is spoken of by the scientific term 'atom' isn't established so easily; only with a closer examination of what we mean can we determine in what sense it is and isn't proper to attribute reality to an atom. By breaking down reality into two concepts, we can begin to understand that the same sort of existence attributed to a table cannot be properly attributed to an atom.

Creating a distinction between the word 'reality' and the word 'existence' can serve to draw out two distinct types of being, by lending one of the meanings of reality to the word existence. The choice of which meaning applies to which is somewhat arbitrary, but this is mere semantics. Reality, to put it in the simplest form, is here defined as that which is not fake. Existence is that with which an encounter is comprehensible. Reality contains everything that exists, but existence is only a subset of what is real. Nothing unreal exists, but some things which are real do not exist. Existence is of objects, while reality also covers ideas beyond objects. A number is only real, while a baseball exists. The gross national product is only real, while Antarctica exists. The probability of the sun not rising tomorrow is real, while the sun itself exists.

While existence is narrower than reality, it should not be made too narrow. It would be a mistake to say that for something to exist it must be possible to go out and observe it. Taking existence in that strict sense the planet 51 Pegasus would not exist simply because with current technology we have no way to see it... clearly this wouldn't make sense, as it would have things popping in and out of existence depending on our own capabilities at a particular time. Even in cases where we haven't yet derived the existence through any means, so long as we can imagine that it would be coherent to call the thing an object we can satisfy the metaphysical criterion for existence (and are simply left with the epistemological question of it the imagined object is actually out there). In the case of anything which cannot be coherently thought of as an object -- where the form "if I were to be there, I could sense this" simply cannot apply -- we cannot say that the thing exists. A number (in the sense beyond numeral) cannot be a sense object and so does not exist... there's no place to go to look for a number. Anything which has no spatio-temporal meaning (and thus no "there" to be at to observe) cannot be said to exist. Anything which is not an event itself but instead a probability of events cannot be said to exist. Such things can be real if properly derived out of experience, but they do not exist.

Having made this distinction between reality and existence, we must defend the usefulness of splitting these concepts. Paul Churchland argues observational ontology is "exactly as dubious as non-observational ontology", but a closer examination shows important differences. [1] If Churchland means to point out that the senses don't provide absolute access to the nature of things as they are in themselves, then certainly that's correct... however, transcendental reality is not what we should be asking for from observation. What we need from observation in order to form a proper scheme of truths (along coherentist lines) is simply consistent representation. Despite occasional optical illusions and sensory gaps, experience seems to indicate that the senses provide remarkably consistent data. Even where sensory data is inconsistent, rectifying the mistake is usually as simply as performing more observations under slightly different conditions. The more important point, however, is that the senses are the starting point from which any reality is constructed and any flaw in the senses which isn't correctable by further observation would be passed on into the non-observational ontology. Arthur Eddington phrases the point this way: "Every item of physical knowledge must therefore be an assertion of what has been or would be the result of carrying out a specified observational procedure." [3] Observation is inevitably the supreme court of appeal in science -- the theory which finds no observation to support it is a dead theory. We ask that observation be internally consistent, and we ask that of theories as well... of theories, however, we also ask that they be consistent with observation. Churchland, in missing this point, misses the crucial element of what makes observables more basic to our ontology than non-observables.

With the distinction between reality and existence suitably defended as meaningful, we can apply it to the concept of the atom. The atom, most certainly, is real -- it's derived properly out of observations, just as probabilities and gross national products may be. When examining it under the criteria of existence, however, the atom fails. The nature of an atom as used in science is that it consists of an arrangement of protons, neutrons and electrons. In physics 'atom' is simply the label for an arrangement or activity of these parts, much like a game is a label for an arrangement or activity of people and equipment. To describe what it would be like to observe an atom requires detailing the appearance of the electron, since the electron is the outer part of the atom. The description of the appearance of the electron in physics includes certain interesting properties -- for example, it's incapable of having both a location and a momentum at the same time. Imagine, for a moment, an object which has no location. Now imagine an object which has no momentum (not zero momentum, but rather no concept of momentum). Any idea which comes to mind as an attempt to make this description into something concrete is necessarily wrong. It's not simply difficult, it's logically incoherent to imagine an object lacking a location or momentum. Any idea which comes to mind as an attempt to make imaginable a thing called an atom for which the overwhelming majority of the "space" consists of fields of probabilities of these unimaginable electrons is also necessarily wrong. In mentioning fields of probabilities we also come upon another problem -- the scientific atom does indeed consist of mostly probability fields. While you're imaging either an object which has no location or an object without a concept of momentum, imagine the object not in terms of an event but rather in terms of a statistical probability. This is simply impossible to call an object. As Werner Heisenberg puts it, "the atoms or the elementary particles themselves are not real; they form a world of potentialities or possibilities rather than one of things or facts." [2] The way in which Heisenberg uses the term 'real' (as concrete things or facts, theoretically observable) is the way we've employed the term 'existent.' It's clear by this point that an atom cannot be an object -- the atom does not exist.

Churchland suggests a thought experiment in which there are creatures which have electron microscopes as eyes, and argues that in this scenario the creatures would have no problem saying that atoms exist. [1] Churchland misses a critical point, indeed the central point, with this suggestion. Someone with an electron microscope eye does not see that which science defines and deals with as the atom. The experience of such a person is, perhaps, a series of blue spheres. This experience does not provide the scientific atom at all -- it provides instead a solid spatial and temporal object. This is not the atom described by science. Just as with our macroscopic observations, it would have to be investigated in great detail by science and pulled apart and described in an entirely different way which would seem horribly contrary to experience to for the creatures, in order to do subatomic physics in such a world. The situation is not some practical difficulty to be overcome with better sensory equipment, rather it's a conceptual gap in which the scientific atom defies the very meaning of the concept of an object. The nature of the concept of a chair which people describe and use in life is provided by experience, referring to aspects of the experience itself, and thus we say chairs exist. The atom, in contrast, is unlike any aspect of any experience and becomes incoherent when forced into the idea of experience, thus we cannot say the atom exists.

The illusion that the atom could be an object comes from the fact of it being derived from objects, but being derived from that which exists in no way implies existence. Consider an analogous reality: the odds of the Giants winning the next baseball game played at Pacific Bell Park in San Francisco. Just as the mathematics of the atom are derived out of observations of existing objects, the mathematics of the odds of winning the game are derived out of observations of existing players, tapes of past games, the umpiring crew, the fans, weather conditions, and various other minor contributors. Certainly the odds are real, if they're derived through the proper procedure. We would not, however, want to say that they exist as an object. The odds of the Giants winning are real, but do not exist in the way that the field and the players exist. Some objectors might argue that the atom is more like the game itself -- not strictly definable but still something which obviously exists. The game, however, is said to exist at a moment because the necessary parts of it are all being instantiated on the field, and these parts are all sensory experiences of objects acting. The game exists because it's a label for a way people and objects can interact. The atom cannot derive this sort of existence, because its constituents are even more clearly non-objects than the atom itself. If we could understand the electrons and protons and neutrons as spatially extended shaped objects with positions and momentums, then we could say that the atom (being simply a particular sort of arrangement of these parts) exists... but we cannot understand the parts of the atom in any material sense. For something to exist it must either be an object itself or a label for a grouping of objects, and the atom fails both criteria.

The philosopher-scientist Arthur Eddington explained the situation this way: "To a request to explain what an electron is really supposed to be we can only answer, 'It is part of the A B C of physics.' Science aims at constructing a world which shall be symbolic of the world of commonplace experience. It is not at all necessary that every individual symbol that is used should represent something in common experience or even something explicable in terms of common experience." [3] The atom, along with many other objects of science, is not concrete but symbolic. It is not properly explicable in any experiential terms, yet it serves as an explanation of things which are experienced. Eddington suggests the analogy of a book. "It is like our experience in learning to read," he says. "That which is written in a book is symbolic of a story in real life." Theoretical entities of science are real, in that they symbolize the story of the observational world we live in. This reality, like the reality of numbers and probabilities and symbols of all types, should not be confused with those things which exist in the universe. The reality of a letter plays a part in a word which represents an experience, much like the reality of an atom plays a part in a larger structure which can be thought of coherently as representing an experience. What we must remember is that the reality of the symbol is not in the events of the story, but rather of the story.

Between real extrapolations and existing objects there lies a gulf which cannot be bridged by the imagination. Regardless of if the objective nature of entities fits anything which can be phrased in either form, objects contain the sort of substantiality which we value and also provide the basis from which other realities are derived. No matter how accurately predictive the derivation of a non-observational reality may be, that which cannot be imagined as an object is a distinctly different sort of reality from that which can be imagined as an object. Any attempt at scientific realism must, in one way or another, acknowledge this gap.



End Notes
1: Churchland, Paul. "The Anti-Realist Epistemology of van Fraassen's The Scientific Image"
2: Heisenberg, Werner. "Physics and Philosophy" (p. 186)
3: Eddington, Sir Arthur. "The Nature of the Physical World"