IN nature nothing remains constant. Everything is in a perpetual
state of transformation, motion, and change. However, we discover
that nothing simply surges up out of nothing without having ante-
cedents that existed before. Likewise, nothing ever disappears with-
out a trace, in the sense that it gives rise to absolutely nothing existing
at later times. This general characteristic of the world can be ex-
pressed in terms of a principle which summarizes an enormous
domain of different kinds of experience and which has never yet
been contradicted in any observation or experiment, scientific or
otherwise; namely, everything comes from other things and gives
rise to other things.

This principle is not yet a statement of the existence of causality
in nature. Indeed, it is even more fundamental than is causality, for
it is at the foundation of the possibility of our understanding nature
in a rational way.

To come to causality, the next step is then to note that as we study
processes taking place under a wide range of conditions, we discover
that inside of all of the complexity of change and transformation
there are relationships that remain effectively constant. Thus, objects
released in mid-air under a wide range of conditions quite consist-
ently fall to the ground. A closer study of the rate of fall shows that
in so far as air resistance can be neglected, the acceleration is con-
stant; while still more general relationships can be found that hold
when air resistance has to be taken into account. Similarly, water put
into a container quite invariably "seeks its own level" in a wide
range of conditions. Examples of this kind can be multiplied without
limit. From the extreme generality of this type of behaviour, one
begins to consider the possibility that in the processes by which
one thing comes out of others, the constancy of certain relationships
inside a wide variety of transformations and changes is no coinci-
dence. Rather, we interpret this constancy as signifying that such

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