By Paul Newall (2007)
In his famous work The Mechanization of the World Picture, E.J. Dijksterhuis described in great detail the development of the so-called mechanical philosophy from its origins in antiquity with the Greeks to Newton in more modern times. In its earlier incarnations there were convincing enough counter-arguments that it was not a serious concern to ideas about God. With the rise of experiment as a check on theory, however, mechanical philosophy began to seem more tenable and its possible clash with theological matters more pressing.
Potential problems with the mechanical philosophy were quickly seen by Mersenne, who worried that it might run up against theology and imply that there was no room for miracles. University tutors also became concerned at the consequences that their students were drawing from Descartes' thinking. Nevertheless, the principle difficulty was with God's freedom to act in the world and that free will He had supposedly granted to his creation: if the universe was explicable in mechanical terms – that is, as a machine, running like clockwork, whether crafted by God as great artificer or not – then how could men avoid the inevitable result of the playing out of that design and how could God change it without ruining the structure?
Mersenne had originally favoured mechanistic ideas because he had realised that some form of natural order would be necessary before there could be a miracle that is contrary to nature. For this reason, he advocated the study of nature and the determination of natural laws, but it was easy for critics to associate the supposedly atheistic atomism of the early Greeks with the mechanical philosophy and it was a small matter to move from mechanistic ideas being able to explain the workings of the universe to there being no place left for God, as Laplace would famously remark. Both Mersenne and Descartes believed that God was inscrutable, with the ultimate essence of things forever beyond our capacities; even so, if the mechanistic philosophy was proving valuable in understanding the natural world and the supernatural lies out of reach then it seemed to some that the mechanists were contributing, indirectly or otherwise, to the minimisation or death of God.
How, then, could the mechanistic philosophy be accommodated with a God acting in the world? Descartes chose to ignore the problem, supposing instead that there was no intersection between the domains of faith and nature. This undermined the doctrine of the Eucharist, though, and hence was not considered an option. In an attempt to avoid the more unpalatable consequences of Descartes' work, Malebranche devised the notion of occasionalism, according to which God's direct intervention could be invoked whenever sense-perception was involved; that is, a God actively taking part in His creation at all times and sustaining it. Since it was believed that Descartes' philosophy could explain the workings of nature without any reference to God, his works were placed on the Index of Forbidden Books in 1663, followed by a Royal ban on the teaching of his ideas in French universities.
Gassendi took a rather different approach, believing that he could rehabilitate the doctrine of atomism in a way that would render it compatible with Christian theology; in effect, trying to reduce the barriers between science and religion rather than hold them to be immovable like Descartes. In modern parlance, Gassendi was an instrumentalist, believing that empirical adequacy was the aim of science. Knowledge of causes would remain beyond us, so he defended atomism because it provided a plausible account of the phenomena that Aristotelianism could not; the question of whether God had no role to play in his mechanistic world therefore did not arise, and the issue of whether atomism was "true" or not would not concern him. Some philosophers of science have employed a similar understanding today.
Pascal was deeply interested in experiment and the mechanical philosophy but nevertheless maintained a separation between his work and his theology, demarcating them clearly. Although he believed that the work of God was evident in nature, he held that God Himself was hidden therein rather than manifest. No amount of study of the natural world – on the basis of the mechanistic philosophy or otherwise - could prove the existence of God, then, but neither could it disprove or caution against faith. Pascal, much like Gassendi, was not concerned to show how God interacted with the world because – for both – their understanding of that world rendered the problematic aspects of mechanism moot.
Steno was of a different persuasion: he felt that there was and could be no conflict at all between science and religion. The workings of nature – in his case, geology – could be studied to supplement the Scriptural account; where nature was silent we can appeal to the Bible and where neither tell us anything we can say nothing. He insisted that nature and Scripture could never be in disagreement.
Looking at these five illustrative examples of French natural philosophers we thus find that none of them seem to have exhibited much concern about the compatibility of God with the mechanistic philosophy. Mersenne worried that it might find use in atheistic thinking but felt God to be beyond argument regardless. Descartes ignored the issue and Gassendi did not find there to be a problem at all, if the early atomists were understood correctly. For Pascal, God was hidden and thus under no threat from any implications of experiment or philosophy, and for Steno there was no incompatibility at all. What was never at issue was the belief in God of any of them or the possibility that mechanism might lead to a diminishing of God. They wanted to use the analogy of the clockwork universe to give greater glory to God by coming to know His work, and it is therefore something of an historical irony that those who did most to develop the mechanical philosophy did so in the belief that they were buttressing belief in God.
The issue is subtler, though. Looking again at Mersenne, we find that he was actually concerned to delimit the natural in response to Protestant criticisms that the Catholic Church used miracles to convert people. Mersenne believed in both God and miracles and wanted to employ mechanistic philosophy to show how the former worked through the latter and hence answer the Protestants. To suppose that he found mechanism convincing and then worried that there might be no place left for God is to misunderstand his intent. The mechanistic world would not exclude God or miracles; instead, it would help understand when a true miracle occurred and when it had not. (Note that this is the same motivation that lay behind research into the praeternatural in demonology.)
Descartes was also pursuing a different tack to that we might suppose on a cursory reading. He wanted to emphasise the uniqueness of man by showing him to differ from the rest of creation by the existence of his immortal soul. To do so, he used the mechanistic philosophy to demonstrate that all other regions of the universe, particularly animals, could be understood as machines, however complex. He employed mechanism to make theological points and support the activity of the divine in the world, so it is little wonder that he did not see the consequences that others found in his work. We have already seen that Gassendi felt the question to be one of correctly appreciating what the atomists meant and that Pascal and Steno had nothing to be worried about. For his part, Dijksterhuis saw no link between atomism and the mechanical philosophy, insisting that "a machine presupposes a conscious and intelligent maker who has constructed it and makes it operate to realize a particular object. It is hardly possible to maintain a conception that differs more widely from the worldview of Democritean atomism."
In summary, the issue seems to be that concern at the mechanistic philosophy was on the part of others - those who had read the French natural philosophers considered here but not sufficiently understood their motives and purposes. Leaving these out and considering the thinkers above as examples of mechanistic philosophers is therefore a huge oversimplification; it would perhaps be more accurate to call them natural philosophers who employed mechanism to achieve ends that were their own and not forced upon them by it. Mechanism suited their theological ideas and what they hoped to achieve in their endeavour to bring glory to God.