[38]C. T. R. Wilson, Proc, Roy. Soc., 87, 277, 1912.
We can only conjecture whether the number of fundamental concepts will prove impossible of further increase or not, but present experience seems to give greater probability to the view that as we penetrate deeper the number of fundamental concepts will always tend to become fewer. We have already certainly one example in that the temperature concept disappears when we get to the atomic scale of magnitude, and possibly a second example in the building up of separate concepts for energy and frequency by the combination of great numbers of that one operationally simple thing which characterizes the elementary quantum process in ordinary radiation.
Different sorts of relations between concepts are conceivable in the transition zone where the number changes. We may find that other examples are like that of temperature, which is simply a statistical effect of a great many phenomena which may be described individually in terms of the ordinary concepts of mechanics, so that in this case the number of concepts changes merely by temperature dropping out, leaving the others more or less unaffected. Or all the concepts may be more closely interwoven, so that when the total number of concepts changes it may not be possible to separate out a group of concepts whose defining operations are unchanged. In such a case we must say that the original concepts are not applicable on the new level. The most immediate application of this idea has been already mentioned, namely, to the concepts of space and time. If the operations by which space and time are measured on the ordinary scale of magnitude cannot be carried down as a whole into the region of quantum phenomena, then we must say that the ordinary concepts of space and time are not applicable to these phenomena.
Closely connected with the sharper analysis of the operational structure of our concepts, we may expect in the future also a closer analysis of our inventions. This will take the form of a search for new physical facts which shall give to our inventions the character of physical reality. In case prolonged search fails to disclose such phenomena (as is probably now the case with the field concept of electrodynamics), we must then find some way of embodying explicitly in our thinking the fact that we are dealing with pure inventions and not realities.
INDEX
Absolute, 26
Absolute time, 4
Action at a distance, 46
Analysis of large into small, 51,
220
Arithmetic, 35
Atom, 59
Bell, 84
Birkhoff, 72
Black body, 112
Bohr, 190, 192
Born, 222
Boscovitch, 46
Bothe and Geiger, 116
Bridgman, 201
Brownian movement, 107, 129,
143
Bush, 142
Caloric fluid, 59
Campbell, 117
Carnot engine, 125
Causality, 80 ff
Causal train of events, 85
Clifford, 28
Clock, 70 ff, 176
Compton, 116, 188
Continuity, 94
Conservation of charge, 135,
136
Conservative functions, 113
Constructs, 53
Correlation, 37
Cosmic units, 182
Cross word puzzle, 202
Descriptive background, 64
Determinism, 114, 209 ff
Discontinuous space, 191
Döppler effect, 166
ds, 72
Eddington, 93
Einstein, vii, 1, 2, 3, 4, 7, 8,
9, 12, 13, 14, 64, 100, 155,
162, 163, 164, 167, 169, 170,
171, 172, 173, 175, 176, 177,
206
Electrical concepts, 131 ff
Electrical explanation of
universe, 50
Electrical mass, 139
Electric field, 56, 133
Empiricism, 3
Energy, 108 ff, 126 ff
Euclidean space, 14, 15, 16, 18,
23, 52, 61, 67
Event, 95, 167
Explanation, 37
Explanatory crisis, 41
Extended time, 77
Faraday, 44, 57, 58, 209
Final explanations, 48
First law of thermodynamics,
126 ff
Force, 102 ff
Foucault pendulum, 180, 184
Fourth dimension, 74
Future, 222
Gauss, 15, 34
"Go and come" time, 112
Gravitational constant, 91
Haldane, 25
Heat flow, 130
Heisenberg, 222
Hertz, 44
Hoernlé, vi
Identity, 91 ff
Isolation, 82
Joule, 124
Kelvin, 45, 110
Kinetic theory of gases, 40
Lagrangean equations, 112
Larmor, 149
La Rosa, 164
Length, 9 ff
Lewis, 166, 201
Light, 150 ff
Local time, 75
Lorentz, 143, 147, 148, 149
Mach, 183
Mass, 102 ff
Mathematics, 60 ff
Maxwell, 44, 58, 112, 137, 148
Meaningless questions, 28 ff
Measurement approximate, 33
Mechanism, 45
Mercury, 105
Michelson, 15, 26
Michelson and Morley, 66
Models, 45, 52
Newton, 4, 110
Operational character of
concepts, 5
Operational thinking, 32
Optical space, 67
Ostwald, 109
Penumbra, 34
Perrin, 107
Physical reality, 59
Planck, 69
Poincaré, 48, 115, 116, 190
Pythagoras, 61
Quantum act, 156
Quantum theory, 40, 47, 186
Radiation and temperature, 123
Relative character of
knowledge, 25
Relativity, 150 ff
Reynolds, 93
Rotational motion, 178
Russell, 205
Schrödinger, 222
Space, 66
Silberstein, 11
Simplicity of nature, 198
Simultaneity, 7, 8
Spring balance, 103
Statistical methods, 115, 117
Stress, 54
Swann, 204
Table top, 106
Tactual space, 67
Temperature, 118 ff
Thermodynamics, 117
Thing traveling, 101, 152, 157,
164
Time, 69
Tolman, 201
Truth, 78
Turbulent motion, 120, 124
Velocity, 97 ff, 213 ff
Velocity of light, 100
Whitehead, 167
Wilson, 224