Causality

ARISTOTLE: THE FOUNDING FATHER

We may consider Aristotle to be the founding father of causal thinking. He was a philosopher who distinguished many types of causes (e.g., causa materialis, causa formalis, causa efficiens, and causa finalis). In modern science of the 17th century, his causa efficiens or labor cause became the guiding if not the [Page 103]only principle. Causation was then associated with “production.” The labor cause was the active agent, the external power was like the knock with a hammer, and the effect was that which undergoes in a passive way, like the chestnut that bursts into pieces. This notion of production is present in Newton's external power, which brings a resting body into movement. It is also present in social policymaking. For example, policy-makers in France in the 19th century started a policy of raising the birth rate and of encouraging immigration to establish an excess of births over deaths, so that the aging population structure could be reversed. It is also present in the stimulus-response scheme of the school of behaviorism. And it is even present in our language because many verbs such as poison, cure, calm, humidify, and illuminate contain the idea of production.

GALILEI: NECESSARY AND SUFFICIENT CONDITION

It was also in modern science that cause was clarified in terms of a necessary and sufficient condition by Galilei, where necessary means “conditio sine qua non” or “If not X, then not Y,” and sufficient means “If X, then always Y .” (One should notice that “X necessitates Y ” means “X is a sufficient condition of Y .” Confusion is possible here!)

DAVID HUME: A TURNING POINT IN HISTORY

David Hume in the 18th century is really a turning point in the history of causality. In fact, no author today can still write about this subject without first discussing Hume. An outstanding example is Karl Popper (1972), who, in his book Objective Knowledge, has a first chapter titled “The Hume Problem.” Hume was not against causality (see Hume, 1786). He believed that the world was full of it. But he was skeptical about the possibility of science getting insight into the question of why a cause is followed by an effect. His starting point is purely empirical. He argued that knowledge of causal relations was never brought about in an a priori fashion by means of pure deduction but that it was totally based on experience. Adam could not deduce from seeing water that it could suffocate him. Hume also believed that causes were external to their effects. If a billiard ball collides with a second ball and the latter starts moving, then there is nothing present in the first ball that gives us the slightest idea about what is going to happen to the second one. As for the middle term in between cause and effect (i.e., the causal arrow), Hume stated that such concepts as production, energy, power, and so forth belonged to an obscure philosophy that served as a shelter for superstition and as a cloak for covering foolishness and errors. We see the fire and feel the heat, but we cannot even guess or imagine the connection between the two. We are not even directly conscious of the energy with which our will influences the organs of our bodies, such that it will always escape our diligent investigations. The question of why the will influences the tongue and the fingers, but not the heart and the liver, will always bring us embarrassment. And the idea that the will of a Supreme Being is responsible here brings us far beyond the limits of our capabilities. Our perpendicular line is too short to plumb these yawning chasms. He concluded that when we saw both the cause and the effect, then there would be constant conjunction. After some time of getting used to this, custom arises. And then, via some mechanism of psychological association, we gradually start to develop a belief. And on the basis of this belief, we use causal terminology and make predictions. In short, the only thing that really exists is constant conjunction (regularity theory); the rest is psychology. Loosely speaking, correlation is the matter; the rest is chatter.

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