THE PRINCIPLES OF SCIENCE 199 



If legend may be trusted, Newton's entire gra\dtational theory 

 originated in the speculation that the fall of the apple and the "fall" 

 of the moon in its orbit have one and the same cause. Let no man 

 presume to declare the search for causes unessential to Newton's 

 work. Leaping all the way to Planck, at the beginning of the present 

 centLiry, we find still active in him a concern for causality wholly 

 unsatisfied in the establishment of determinism. Studying blackbody 

 radiation, Planck at last discovered a mathematical expression for the 

 variation of intensity with wavelength and temperature. That law 

 reduces blackbody phenomena to determinist order; but Planck 

 sought, beyond this, a causal explanation of how there is produced 

 the behavior his law describes. Pushing on in this endeavor, he ar- 

 rived at the oscillator model that first suggested the occurrence of a 

 quantum of action. And here we meet the crowning irony: the con- 

 ception so first born matures into a quantum mechanics that chal- 

 lenges not only the idea of causality that inspired Planck's work, but 

 even the concept of determinism. 



QUANTUM MECHANICS, DETERMINISM, AND CAUSALITY 



By the testimony of professional metaphysicians, and of scientists 

 who speak as metaphysicians, we are assured that a catastrophe in 

 the domain of microphysics now forces on us a complete re\ision of 

 our concept of causality and determinism. Yet we behold with aston- 

 ishment that scientists still persevere in causal inquiries that, as ever 

 before, terminate fruitfully in conclusions that make no reference 

 to causes. This paradox is at once resolved when we recognize the 

 cosmologic locus of the "catastrophe." The heuristic principle of 

 causality is far less aflFected than a cosmologic conception of deter- 

 minism that, starting perhaps from the God who sees the sparrow's 

 fall, passes on to a Laplacean non-God who precisely foretells the 

 coming of star, dust-mote, and electron. Such an absolute determin- 

 ism of individual events had of course never been attainable in the 

 practice of science, and scientific practice owed but little to it. Sci- 

 ence thus remains undamaged when the cosmologic conception of 

 determinism is toppled by the explosive charge that individual micro- 

 physical events remain forever subject to an irreducible indeter- 

 minacy and unpredictability. But that blast does have some impor- 

 tant repercussions in science. 



