with Plato in his naïve assertion (Timaeus, 37), "God created time, and the parts of time – days, months, and years." But we cannot define time in terms of motion, when motion is defined in terms of time. If beings exist whose rate of thought is entirely variable, they have no science such as ours. If elsewhere in the universe there are rational beings whose rate of thought increases as the square of the time (terrestrial) during which they exist, they may have a system of mechanics, which would differ from ours in ways possible for us to calculate. It is true the intervals between certain physical changes are more constant than the intervals between thoughts, but this is a discovery made by using changes in thought as a standard of measurement. Indeed, the motions of physical bodies used to measure time are not so entirely accordant as is often assumed. There is no physical fact corresponding to the idea of uniform motion. A consciousness is conceivable to which the movements of the solar system are as irregular as the changes of the weather are to us. As the possibility of mechanics rests on the constancy of the rate of mental change, it is evident that this rate is sufficiently constant to admit of measurement.
10. Length of life is measured by rate of thought.
Should all our suns and pendulums begin to move faster and faster (time being measured by revolution of the siderial universe, and dynamical relations of space and mass being adjusted to fit), and all our thoughts and movements increase at the same rate, it would neither concern us, nor be noticed by us. Should our objective measures of time move faster, while the rate of physiological and mental change remain the same, we should live more days and years before we die, but none the longer. Should we live as many solar years as now, while the rate of thought and movement were increased, we should live so much the longer. The measurement of the rate of thought in the current units of physical science would seem, therefore, to be a matter of considerable interest. We need to know the time of physiological and mental processes, and the conditions
