Causality In Our Material World

Ludwik Kowalski Ph.D.

Section 1

I recently heard a talk about color. The speaker asked "Why do most people say that blue is their favorite color?" This fact has been established by conducting objective surveys, I suppose. I did not know how to answer the question. And I did not pay attention to how it was answered; I was thinking about how I should answer.

"Why is the sky blue?" he then asked a youngster. The boy's answer, based on what he learned in school, was more or less correct. This made me think about what "why" stands for, and about how it should be answered in general. How can we distinguish an answer that is acceptable from one that is unacceptable? Do all questions have acceptable answers?

Suppose someone asks me "why does the shape of the moon change from week to week?" The answer "because the illuminated part of the moon, visible to us, changes" is certainly acceptable (to those who have learned about stars, planets and moons.) But the question "why is it snowing in our park today?" is much more difficult to answer. In fact, I am not sure it can be answered without referring to the notion of probability.

According to one philosopher, everything in the universe has a cause and is thus an effect of that cause. A single cause-and-effect chain, schematically diagramed in Figure 1, has been engraved in my mind since childhood.

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Figure 1

It is a model of reality shared by many people. Circles represent events and arrows stand for links between them. The event to the left of an arrow (simultaneous or earlier in time) is a cause while the event to the right is a consequence. The implication is that events can be explained. Arrows in the diagram can be viewed as acceptable explanations, i.e. logical theories consistent with objective reality.

"Why do oxygen and hydrogen bubble out from a solution of salt in water, when an electric current flows through the solution?" Our answer today is "because water is made of atoms of oxygen and hydrogen, and because the electric current ... ." It is interesting that the idea of everything "being made of tiny invisible atoms" was introduced by ancient Greeks, long before oxygen and hydrogen were discovered. To them atoms were nothing more than a hypothesis.

Section 2

The above diagram does not imply that all events in the universe belong to one chain. Event C, for example, can also be due an event in another chain. A better diagram is shown in Figure 2 below. It illustrates a more realistic situation in which chains are tangled. A single event is most often due do several different causes. Likewise, a single event usually influences more than one event. Reality, in other words, is more complex than a simple model. Models are only approximations of reality.

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Figure 2

Another interesting topic has to do with real versus fictitious causes. Why do people pray for rain, for example? Because they believe that praying for rain can cause rain. There is advice about this (in a prayer book); it states: "pray as if all depended on God but act as if everything depended on you." This can be interpreted in several ways. My interpretation is based on the idea of NOMA, formulated by the biologist S.J. Gould (1). I even wrote an article about this; it has been published recently in American Atheist (2).

Section 3

The link to the above two sections was "advertised" over the Internet; I often do this to generate comments. On 6/18/2012 I wrote: "Some of you might be interested in my very short article about causality." One reader wrote:

"I wouldn't even say your second diagram is correct. No cause can be linked with its effect absolutely. For instance, when we observe a match being struck to produce fire, we cannot be certain that the striking of the match was the actual cause of the fire. Our minds merely observe a succession of events - first, the match being struck and, second, the flame erupting into being - and it is only through our past experiences of watching a similar succession of events that enables us to assume the two are causally linked. But we can never be sure that this assumption is valid. The fire might well have been produced by something else entirely, ... "

A second reader wrote:

"I believe in chaos theory, I don't think every action can be explained. If everything has some cause, then explain me this, what is the cause for this all, I mean the universe, that imply god is involved ..."

I agree with the first reader; "a succession [or simultaneity] of two events" does not necessarily imply causality. Suppose it is raining (event X) and a rainbow appears (event Y). I claim that X is the cause of Y. How do I know that the opposite is not true? My claim is justified by understanding of optical refraction, the prism-like effect in raindrops.

We say that Y is a possible consequence of X when the occurrence of X might lead to the occurrence of Y. The use of the term “might,” rather than “must,” is deliberate. Some events lead to several consequences and some consequences result from more than one event, as illustrated in Figure 2.

Causality is a principle according to which humans are able to explain events scientifically. The second reader seems to think that everything is chaotic, rather than predictable. This is not consistent with science; we know that some events, such as solar eclipses, are highly predictable.

Section 4

The term “event,” in Section 1, refers to what happens in our material world. Likewise, the terms “real” or “fictitious,” at the end of Section 2, refer to theories that are “accepted” or “not accepted” by scientists. A scientific theory is a man-made logical structure. Unlike a speculative assumption (hypothesis) a theory is based on confirmed experimental data. Theories are satisfactory explanations of such data. Arrows in the above two figures refer to accepted theories. A theory that explains only one or two experimental facts is not as strong as a theory explaining five or more such facts. The ultimate test of a theory is in its a bility to predict.

But theories are not carved in stone. Even a very strong theory, often called a law of nature, is falsifiable. A conflict between a confirmed experimental fact and an existing theory would lead to a modification or abandonment of the theory (3,4). Scientists know the rule-theories guide but experiments decide. But they are very reluctant to abandon accepted theories. To be reluctant means to insist on additional verification of new experimental results. The ability to identify and understand causal relations, which can be either deterministic or probabilistic, is essential in the practical activities of scientists, engineers, medical professionals, money managers, etc.


1) Gould, S. J. (1997). "Nonoverlapping Magisteria." Natural History 106 (March): 16-22.
Also online Click to see it.

2) Kowalski L., “
Futile Confrontations Between Theists and Atheists;" American Atheist, First Quarter, 2012.
Also online Click to see it.

3) Popper K.R. “Science as Falsification;” 1963.
Online at: Click to see it.

4) Kuhn T.S. "The Structure of Scientific Revolutions." University of Chicago Press, 1996.