Out of Sight... Out of Mind? A review of two articles on the ontological status of theoretical entities

The question of the existence of theoretical entities is the subject of W. T. Stace's article Science and the Physical World and Grover Maxwell's The Ontological Status of Theoretical Entities. Theoretical entities are things that are unobserved, either because they are sub-microscopic (electrons, neutrinos and the like), or because they simply do not exist in a traditional sense (gravity, warped space-time). We are unable to directly perceive these entities with our five senses, and therefore they would seem to consist of something other than what is tangible to our touch, taste, sight, hearing or smell. What then do these entities consist of? How can their existence be verified? What is their purpose? We shall see what both these philosophers of science think of these questions, and I will attempt to synthesize both positions into a coherent conclusion.

Stace

Stace begins his article by asking an intriguing and often overlooked question; how are we to know that the unobserved phenomena in science (such as electrons, protons, neutrons) really exist? They are inferred from measurements that we can directly perceive. This is a causal inference, one event must be present in order to "cause" the second to occur. However, Stace argues that this viewpoint is invalid because all our "causal laws" are based upon direct observation. In fact, Stace says "... we have not got, and never could have, one jot of evidence for believing that the law of causation can be applied outside the realm of perception..."(p.353), in other words, there is no sensation associated with the presence of electrons or protons, so how can their existence be causally inferred? They cannot maintains Stace, and therefore "... we cannot have any reason at all to believe that the exist." (P.353).

Stace must then ask, are these theoretical entities false and untrue, completely worthless? His answer is definitely not. He uses the analogy of a nautical almanac, wherein the entries do not exist in any physical sense except on the pages of the book itself. Yet, these entries are true in that they allow us to predict certain sensations (the positions and times of the stars). Stace is suggesting that theoretical entities are nothing more than "shorthand formulae" (p.353), which enable us to explain or predict certain phenomena. Here Stace gives the example of gravity to clarify his point; Newton's Law of Gravity (which was nothing more than a mathematical formula) governed the operation of the "forces" associated with gravity. With the advent of a relativistic space/time continuum, these forces were no longer thought to exist. However, the law can still be applied without the belief in these forces in order to predict planetary phenomena. In other words "It is a matter of no importance to the scientific man whether the forces exist or not." (P.354). Stace believes that the question of whether or not these theoretical entities exist belongs with the philosophers of science and furthermore, they should pronounce these entities as fictions that are sometimes useful for making predictions or explanations.

Stace touches upon the reasons humankind has for inventing these entities such as "forces" or "space-time warps". He posits that humans cling tenaciously to the belief that science "explains things", not content with a description of events, we need to know why something occurs. Unfortunately for us, "...scientific laws, when properly formulated, never ‘explain' anything" (p.355). Laws simply state that under the proper antecedent conditions, when A happens, B always happens too. Stace places atoms within the same context as gravitational "forces", being simply mathematical formulae that are scientific ways of stating what will occur in certain situations. Just as humans demanded that gravity be made a "real thing" with the inclusion of "forces", the demand for a "real thing" corresponding to atomic formulae brought about the notion of the atom.

Followed to its logical conclusion, Stace's article asserts that the entire question of existence is a moot point. All that actually exists are sensations and the minds that perceive them, the rest of "reality" consisting of mental constructions or fictions. Stace does point out that this doesn't necessarily mean that terms like "electron' or "atom" are worthless, they are "useful fictions". Their value lies in their capacity to organize our experience and to predict sensations associated with these phenomena. In the end, these entities are not causal agents for sensations, and sensations are not necessarily proof of these entities' existence.

Maxwell

Maxwell's emphasis is immediately on the Instrumentalism vs. Realism debate in science studies. He aims to demolish the "straw man" of the Instrumentalist/Realist dichotomy. Maxwell quotes Professor Ernest Nagel as saying " The Instrumentalist's position on theoretical entities is that they are instruments for making predictions or confirmations. On the other hand, Realists would say that these entities are objects of some type"(p.365). Maxwell uses a fictional entity he calls "crobes" to illustrate the four prevailing views on the status of such entities:

1. Theoretical entities are convenient fictions (they do not exist)
2. The existence of these entities is reducible to talk about sense-data or everyday physical objects (they exist only if they can be reduced to things that "actually" exist) (also called Reductionism)
3. Theoretical entities are mere calculating devices (they do not exist, but allow for prediction)
4. Theoretical entities exist (Realism)

Maxwell then goes further by asking what would happen if suddenly we could "observe crobes" under a microscope powerful enough to resolve them. The responses noted above must obviously change with this new information. An interesting possibility about the microscopic discovery is introduced when Maxwell has us imagine that "... the crobes were not observed at all; it was argued that what was seen by means of the microscope was just a shadow or an image rather than a corporeal organism."(p.366). This possibility of the microscope somehow distorting reality is countered by Bergmann's analysis "But it is only fair to point out that if this ... methodological and terminological analysis ... is strictly adhered to, even stars and microscopic objects are not physical things in a literal sense, but merely by courtesy of language and pictorial imagination."(p.366). Maxwell responds with the notion that any person wearing glasses or looking through a window would then be seeing only imaginary depictions of reality, an awkward result at best. So where does one draw the line between "actually seeing" something and "seeing shadows" in a microscope lens? Maxwell argues that there is a continuous transition from the observable to the unobservable.

In Maxwell's view, a theory enables us to know what exists and what does not. However, this entails a theoretical/observational distinction, precisely what we are trying to do away with. Therefore, theory may tell us what exists, but the continuum from observational to theoretical is an unbroken line. This however, suggests that the theoretical and observational statements cannot be different without explaining how exactly a theory may tell us what exists. The next step is to say that only those entities which are in principle impossible to observe are theoretical entities, and therefore do not exist. Of course, new problems arise from this reasoning: how are we to determine what is impossible to see? (New optical techniques may become available, for example) Also, how can something impossible be useful?

Maxwell draws his distinction not between observational and theoretical, but between observed and unobserved. Maxwell says that our observation language must not have too narrow a view, or else each language user would have a different observation language. The language must be broader, and observation terms should be a member of some more general type, the specific type to be determined by either science or language. The problem here is that wider groups can always be made, blurring the sharp distinctions that science favours. Maxwell delimits this compartmentalism by suggesting Feyerabend's "quickly decidable sentence". That is, a non-analytic sentence such that a competent language user can quickly decide to assert or deny what is being reported. This makes a new definition for an observation term: "A descriptive (nonlogical) term which may occur in a quickly decidable sentence"(p.371). Maxwell concludes his essay by stating that our drawing of the observational/theoretical distinction was an accident due to our physiological makeup, current state of knowledge, and current technological level of instrumentation. Therefore, the observational/theoretical dichotomy has "no ontological significance whatever..."(p.372).

In conclusion, both Stace and Maxwell seem to agree that there is a problem with the current view of theoretical entities. Stace says that theoretical entities are short-hand formulae that enable us to explain and predict phenomena. Further, even observable entities are sensations perceived and interpreted by people's minds, and therefore these are "useful fictions" used to communicate sense-data impressions between observers. Maxwell holds a similar view, however, his emphasis is on language, and the terms used to communicate observational and theoretical sense-data. His ideal explanation consists of "quickly decidable sentences" that can convey sense-data perceptions in a reliable way. Both Stace and Maxwell would agree that the distinction between observational and theoretical should be reevaluated, and a synthesis of both their positions would seem to be the most complete and comprehensive view to adopt.

Bibliography

ed. Klemke, E.D., Hollinger, R., Rudge, D.W. Introductory Readings in the Philosophy of Science 3^rd edition, Prometheus Books, New York 1998