CHAPTER FOUR 53 THE WORLD OF PHYSICAL SCIENCE
SINCE the crucial difficulty with the religious world-view today is its alleged inconsistency with the conclusions of modern natural science, it will be necessary as a first step to say something about the scientific world-view. Our present purpose does not call for a complete statement of this view, even in general outline; if such is desired it can easily be found in books on the subject written by competent scientific authorities. I shall be content with a brief reference to certain outstanding features of the scientific conception of the world which are of importance to our inquiry.
The first thing we have to notice is that the scientific view of the world is not, and
53
THE RELIGIOUS RESPONSE
54
does not purport to be, a description of existing objects as we encounter them in our ordinary experience of the world. It is an explanation or interpretation of the objects and events of the experienced world in terms of a selected group of attributes or properties. The properties selected are the material or physical qualities, what we commonly mean by matter and motion.
It is sometimes said that physical science disregards all the innumerable differences of quality which objects display. Perhaps a truer statement would be that it translates or reduces these qualitative differences into differences which can be quantitatively determined and coordinated. Even the slight acquaintance which we all have with scientific methods and conclusions is sufficient to afford illustration of this. Differences in color and in brightness science reduces to differences in length, amplitude and form of light-waves,
THE RELIGIOUS RESPONSE
55
differences in tone to differences in rate, amplitude and form of air-vibrations, and differences in taste, odor, temperature, and the like, to differences in the physico-chemical reactions of the sense organs to variations in the physical stimulus. Thus qualitative differences disappear from the world and with them goes the most of what we find interesting and valuable in existing objects. In place of the world we perceive with its rich diversity of colors and sounds, of tastes and odors and textures) of pleasant warmth and scorching heat and freezing cold, science offers us a system of moving particles which weave by their regular motions patterns of increasing complexity beginning with the atom and extending to stellar systems and galaxies which traverse the illimitable abysses of space. The atom, which was for long accepted as the ultimate physical unit, turns out to be a planetary system containing a positively charged nucleus
THE RELIGIOUS RESPONSE
56
around which revolve a number of electrons or negative charges. Qualitative differences supposed to hold between different sorts of atoms, the “elements” of chemistry, turn out to be based on, or reducible to, the number of electrons which rotate about the central nucleus. Through a crossing of the paths of their outermost electrons, atoms become entangled and constitute molecules. Out of such clusters of entangled atoms the things we recognize and deal with are composed. Increasingly extensive physical complexes give us planets with their satellites and stars and nebulae.
Scientific explanation of the world is thus an explanation of the character and changes of existing objects in terms of their geometrical and mechanical properties. The said properties are extension in space and time, motion, inertia or mass, and force. As a system of mass-points in regular motion, science
THE RELIGIOUS RESPONSE
57
understands the world. Now what advantages does it gain by singling out these properties and disregarding all others? The answer is that objects in their geometrical and mechanical properties have simple and constant relations which are capable of exact quantitative determination and mathematical statement. For objects in their size, shape, and movement are measurable and to measure is to discover a precise and constant quantitative ratio between two magnitudes determined by the number of times one contains the other. So when we say an object weighs five pounds, the number 5 symbolizes a constant quantitative relation between the object in question and a pound weight. Measurement is the first essential of scientific explanation. When such precise quantitative determinations of different sets of events are made, the investigator is in a position to detect relations of correspondence or concomitant variation between
THE RELIGIOUS RESPONSE
58
them. When Kepler discovered the orbits of the planets to be ellipses of which the sun occupies one focus he was able to prove that the rate or time of planetary movement was proportionate to the area swept by a radius vector from the planet to the sun. Such uniformities of relation between classes of objects or events which have been quantitatively defined and determined are what we call “laws” of nature, a “law” of nature being nothing, as the scientist reminds us, but a description in terms at once general and exact of the way in which objects behave, or events occur. But explanation by physical law, be it noted, always consists in explaining the movement of one class of bodies by its determinate quantitative relation to the movement of another class of bodies, and ultimately by its relation to the whole interlocking system of regular motion by which its own movement is completely, determined.
THE RELIGIOUS RESPONSE
59
While all this applies to the science of physics and the type of explanation which it offers, does it hold true of all other natural sciences? Physics is after all but one of the natural sciences; there are many others: chemistry and astronomy and geology and biology and anthropology and psychology. As far as chemistry is concerned, it is now generally admitted that the phenomena which it investigates, of “chemical reaction,” are ultimately explainable only by the physics of the atom. In astronomy and geology the only type of explanation regarded as final is that in terms of physico-chemical law. The biological sciences are more debatable ground, it is true;
the question whether the forms and processes of life can be explained scientifically in other than physico-chemical terms is a subject of dispute among biologists themselves. But since both parties agree that many vital reactions can be explained physico-chemically, and a
THE RELIGIOUS RESPONSE
60
large, influential group of biologists believes that we shall never have a true science of the living organism until all its processes are explained physico-chemically, it does not seem necessary to make an important exception of biology and its allied sciences. Hence we seem to have sufficient reason for treating such explanation as we have been considering--explanation by physical law and in exact mathematical terms--as the method characteristic of modern natural science.
Enough has been said, I trust, about the nature and methods of scientific explanation to establish the first point. This was that science explains the existing world not by discovering relations and connections which we can all observe between the objects of our common perception, but by interpreting the objects and occurrences we perceive as due to the behaviour of objects which are imperceptible and can be conceived or pictured only by
THE RELIGIOUS RESPONSE
61
the scientific imagination, such as atoms, electrons, radiant energy, fields of force, etc. Despite the fact that these scientific objects and forces cannot be directly perceived, science does not doubt that they really exist, that they in fact constitute the reality of the world of common perception. Why is this?
The reason, of course, is that while the objects and processes by which science explains the changes that occur in the actual world cannot be directly perceived, their existence and operation can be indirectly verified by observation and experiment. If we are to understand the meaning of scientific verification, however, we must not think of the observation to which the scientist appeals as merely a passive looking, to which experimentation is an incidental aid. To guard against this misunderstanding it is perhaps better to think of the method of scientific verification as primarily that of experimentation, i.e., the
THE RELIGIOUS RESPONSE
62
manipulation and control of observed objects and forces. Measurement, which, as we have seen, is the first step in scientific investigation, always involves some kind of manipulation, depending of course upon the instrument employed. In the simplest and, in some ways, the typical case of applying the measuring rod, we compare two objects in respect to one dimension by juxtaposition.
Observation as the final court of appeal in scientific verification always involves a program of action varying from a few preparatory adjustments of the body and sense organs of the observer, to a lengthy, detailed, and complicated course of laboratory procedure requiring the use of special instruments and technique. A definitely prescribed program of action which can be repeated by the observer or by other observers at will is what we call an experiment. Now what suggests in the first place such a program of
THE RELIGIOUS RESPONSE
63
action, and what directs the course it is to take? It is suggested to the mind of the investigator by an anticipatory idea of certain changes which will be perceptible somewhere, sometime, in the actual world, in consequence of a uniformity of relation or law which he has been led by previous observations and experiment to suppose exists in the world of nature. This anticipatory idea, or “hypothesis,” dictates his preliminary movements and manipulations. These may be brief and simple or prolonged and difficult, but their outcome is to put the investigator in a
p position to make a direct and decisive observation. And it is this which either verifies or disproves the supposed uniformity of relation which is under test. If the facts as perceived from the point of vantage gained by the series of preliminary movements beat out the anticipation of the investigator, his hypothesis within the field of its intended application
THE RELIGIOUS RESPONSE
64
stands verified and is accepted as true to fact. This agreement may be direct, in which case what is perceived carries out or reproduces with greater vividness and fullness of detail the connection or sequence which the investigator has anticipated in imagination, as when certain paths of motion or structural patterns appear in the field of the microscope. Or it may be indirect, in which case the facts which observation discovers serve to reproduce or confirm certain consequences of the supposed laws, previously deduced and kept clearly in mind, as when the bending of light rays, or the shifting of lines in the spectrum, bears out some far-reaching physical hypothesis.
The conclusions of physical science are accepted as true, therefore, and its laws as really existing, because they enable us to predict what we shall find in advance of actual observation, to anticipate the course of nature
THE RELIGIOUS RESPONSE
65
and thus to gain a measure of control over its processes.
Three salient facts have emerged from this brief discussion of the scientific view of the world:
First: Science explains the world altogether in terms of its primary or physical properties, extension in time and space, motion and mass. It conceives of every change in existing objects as due to the motion of mass-points or energy-units, and understands every motion of every particle to be proximately caused by the motion of some other particle and ultimately by the universal or cosmic system of regular motion.
Second: The first and essential condition of such explanation as science undertakes is enumeration and measurement. By the practical art of measurement various objects and occurrences are reduced to multiples of some fixed quantitative unit. Thus each different
THE RELIGIOUS RESPONSE
66
object or event is determined quantitatively by, its position in a series constituted by the repetition of an identical unit: inch, foot or mile, linear, square or cubic; second or minute or hour or years; miles per hour, vibrations per second, etc. Between these quantitative determinations of different classes of objects or events, correspondences and uniform variations are discovered and symbolized in mathematical equations which stand as exact indices of the causal dependence of one physical event upon another in the mechanical system.
Third: The conclusions of physical science are accepted as true, its laws as really holding. because they enable the investigator to predict what events will occur in advance of present perception, in this way to anticipate the course of nature, and so to gain a measure of control over its processes.
