Fr. William A. Wallace, O.P., The Modeling of Nature: Philosophy of Science and Philosophy of Nature in Synthesis (Washington, DC: The Catholic University of America Press, 1996), 252-254.

Modeling the Real

The modeling value of theoretical concepts may be illustrated with the aid of a homely example, that of the “mermaid.” It is sometimes said that mermaids were thought to exist because sailors, after long months at sea and when observing under adverse conditions of distance and at dusk, saw beings nursing their young at the breast, with long hair and fish-like tails that came into view when they dove beneath the surface. To explain these appearances, the sailors constructed an explanatory concept by putting together two concepts of which they had previous experience, namely, “fish” and “woman,” and arrived at the construct “mermaid.” On this account “mermaid” became a candidate for existence, but not existence in a complete and absolute sense, because the sailors were sure that they had observed something, though they were not sure of what it was. Their problem focused on the nature rather than on the existence of what they had seen, and hence their construct was formulated to explain the entity’s nature rather than its existence. The problem was ultimately solved with the identification of a species called the dugong, which, when viewed under conditions approximating those of sailors at sea, were found to explain the phenomena they had observed. Dugongs nurse their cubs at the breast, they have blubber around their necks that in silhouette conveys the impression of long wavy hair, and they have tails like those of fish.

A somewhat similar situation exists with the theoretical entities known as elementary particles, an example of which would be the electron [...] The “electron” is a very useful concept for explaining electrical and magnetic phenomena, to say nothing of light and colors, such as the yellow beam emitted by the sodium atom [...] As a theoretical entity it enjoys a status much like that of the “molecule,” for it is now generally accepted among scientists as having extramental existence [...] But some years ago, when trying to discover more about the nature of electrons, investigators encountered puzzling phenomena, including some in which electrons behave like waves and others in which they behave like particles. To explain these phenomena they formulated a construct that combines features of both, and so gave rise to the theoretical concept “wave-particle.” Obviously, one can go on from this and formulate a proposition such as “The electron is a wave-particle.” And “wave-particle” turns out to be a very useful construct, for it suggests numerous calculations and predictions that can render an account of the metrical aspects of electronic phenomena, most of which can be tested experimentally and verified [...] Yet despite such extensive verification, “wave-particle” remains a problematic concept [...] Its status is only probable, even though the existence of the entity designated as an electron may be quite certain. The point to be made, therefore, is this: granted that “wave-particle” does not tell the whole truth about the electron, it does furnish an insight into what an electron might be. It is in this sense that “wave-particle” might be thought of as modeling the electron in much the way “mermaid” functioned in a preliminary modeling of the dugong.

Theoretical constructs of this type are useful for investigating the domain of the very large as well as that of the very small. For example, it is generally acknowledged that planets and stars are massive objects in the heavens, that they have weight or gravity. Now, although “weight” and “gravity” are concepts that seem to be well understood, the cause of gravity has turned out to be more problematic. In that connection Newton spoke of “gravitational attraction” and even speculated as to whether or not the “pull of gravity” is real, but he did not commit himself to a definitive answer [...] Some two and a half centuries later, after having studied gravitational phenomena more extensively, Einstein proposed a quite different explanatory concept. He did so by adopting a suggestion of his teacher Hermann Minkowski, who took the two well-known concepts “space” and “time” and combined them to formulate the theoretical construct “space-time” [in his 1908 address, “Space and Time,” translated and reprinted in The Principle of Relativity, New York: Dover Publications, n.d., pp. 73-96]. From this followed mathematical calculations and predictions, much like those generated by the construct “wave-particle.” These have subsequently been verified, and they give “space-time” a probable status analogous to that of “wave-particle.” Yet one need not hold that “space-time” is fully real [...] It is generally acknowledged also that such a construct furnishes some insight into the reality behind gravity and gravitational phenomena, much as did Newton’s earlier construct of “pull of gravity” that dominated physics throughout the eighteenth and nineteenth centuries.

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Return to Lesson 3: The Scientific Method: Its Benefits & Limitations