III The Mechanical Interpretation of the Universe

that Helm Holtz declared that ‘the final aim of all natural science is to resolve itself into mechanics,’ and Lord Kelvin confessed that he could understand nothing of which he could not make a mechanical model. It was the age of the engineer-scientist, whose primary ambition was to make mechanical models of the whole of nature. Although scientists had not yet succeeded in explaining all of the manifestations of this universe according to this principle, this want of success failed to shake the belief that the universe must in the last resort admit of a purely mechanical interpretation. It was felt that only greater efforts were needed, and the whole of inanimate nature would at last stand revealed as a perfectly acting machine. All this had an obvious bearing on the interpretation of human life. Each extension of the law of causation, and each success of the mechanical interpretation of nature, made the belief in free-will more difficult. For if all nature obeyed the law of causation, why should life be exempt? Out of such considerations arose the mechanistic philosophies of the seventeenth and eighteenth centuries. Science appeared to favour a mechanistic view which saw the whole material world as a vast machine. Then came the discovery that living cells were formed of precisely the same chemical atoms as non-living matter, and so were presumably governed by the same natural laws. This led to the question of why the particular atoms of which our bodies and brains were formed should be exempt from the laws of causation. It began to be fiercely maintained, that life itself must, in the last resort, prove to be purely mechanical in its nature. The mind of a Newton, a Bach or a Michelangelo, it was said, differed only in complexity from a printing press; their whole function was to respond exactly to the stimuli they received from without. But science today does not adhere to this rigid and unbalanced principle of causation. The theory of relativity calls the principle of causation an illusion. At the end of the nineteenth century, it was first revealed to science that many of the phenomena of the universe, radiation and gravitation in particular, defied all attempts at a purely mechanical explanation. While philosophers were still debating