Only a fool would deny that the application of mathematical techniques to the study of nature has proven extraordinarily successful. From determining the acceleration of a body moving towards the ground to predicting the movements of the planets, the knowledge acquired through the use of such techniques as well as the techniques themselves have been rightly lauded. However, despite these many triumphs, further questions can still be asked. For example, whether the mathematical study of nature – in effect contemporary physics – is the only way to study nature? Whether the mathematical study of nature is the only way to study nature scientifically? What form such a study or studies might take if one answers either of the previous questions negatively?
Alister McGrath does not address these matters explicitly. However, it is clear he would deny that the mathematical study of nature was the only way to study nature. Not only does he remark that his ‘proposal is to retrieve or recreate a larger conceptual and imaginative space, enabling deeper and richer conversations about the natural world’ (p. 4), but he also acknowledges the ‘increasingly urgent need of supplementing a scientific approach to the natural world with one that is attentive to wider questions’ (p. 109). The further study of nature thus proposed is a ‘contemporary reconstructed natural philosophy’ (p. 13). Since it merely supplements ‘a scientific approach to the natural world’ (p. 109), it will not be a scientific study itself. Yet its reconstruction combines both historical (chapters 1–5) and systematic elements (chapters 6–10) and might be best interpreted as an answer to our third question.
McGrath’s historical investigation begins with Aristotle. He suggests that Aristotle’s approach depended upon ‘the assumed capacity of the human mind to discern an existing, rather than imposed, order within the natural world’ (p. 18). That seems right, but McGrath emphasises the empirical character of Aristotle’s natural philosophy to such an extent that one wonders how this order can be discerned. For instance, ‘nature’ in natural philosophy designates kosmos rather than phusis (pp. 18–19). So understood, ‘nature’ will not ground a distinction between natural things and artefacts, nor will it allow any appeal to an intrinsic teleological framework. Methodologically, The Physics pursues a ‘largely non-empirical metaphysical approach’ (p. 24), whilst matter and form are regarded as non-empirical (p. 27) and presumably to be rejected. The logical result of all this is that any order to be found in such a world will have to be at the sensory rather than the intelligible level.
The study of medieval natural philosophy in the next chapter continues in a similar vein except that it further specifies the character of natural philosophy. Natural philosophy, we are told, ‘can be pursued independently of theology’ (p. 35) because it does not rely on ‘any special divine illumination’ (p. 36). That seems entirely reasonable, yet a little later natural philosophy is broadened to include to include forms of reasoning which ‘rely on natural capacities and resources’ (p. 36). So much so in fact that natural philosophy becomes ‘a shared common language, enabling conversations across both disciplinary and religious divides’ (p. 35). One is left to wonder how McGrath would distinguish natural philosophy from metaphysics.
The third chapter discusses the changes natural philosophy underwent as the heliocentric model of the solar system supplanted the geocentric model. Copernicus’s, Tycho Brahe’s, and Kepler’s gradual refinement of the heliocentric model receive useful attention, as does Galileo’s telescopic observations and incipient mathematisation of natural philosophy. What is striking, however, is just how damaging this is thought to be for Aristotle’s approach. Thus, McGrath observes that ‘with the erosion of the artificial Aristotelian bifurcation of what we now take to be ‘nature’ as a whole the scope of natural philosophy was significantly extended and enriched’ (pp. 53–54).
Yet this ‘bifurcation’ did not render the celestial bodies and their motions unnatural because Aristotelians recognised that celestial bodies had natural aptitudes for their motions (ScG 3 c. 23). Certainly, these motions were only natural according to matter, but they were still natural, as were the celestial bodies thus moved. Further, the distinction between celestial and terrestrial bodies and their proper motions followed upon the intentionality of nature not upon whether one accepted a heliocentric or a geocentric model of the solar system. Since celestial bodies were thought to move without ceasing but nature tended towards an end, then the rotational motions of celestial bodies could not arise spontaneously from their formal principles. Motion was never for the sake of motion; celestial bodies had to be moved. Terrestrial bodies, however, never moved without ceasing; they always moved towards an end. As such, their rectilinear motions could arise spontaneously from their formal principles unless otherwise inhibited. Unlike celestial bodies, then, the motion of terrestrial bodies was natural according to form.
Chapter 4 examines the development of natural philosophy in the work of Bacon, Boyle, and Newton. It highlights the distinction between speculative and experimental natural philosophy (p. 78) and it helpfully points out the distinction between Newton’s own thought and the way that thought was interpreted subsequently (p. 77). Thus, one can interpret Newton’s famous remark ‘hypotheses non fingo’ to mean he chose to offer no hypotheses about the physical causes of the phenomena he investigated mathematically rather than the claim that there was no need for such explanations. In other words that the mathematical study of nature abstracted from essential features of the natural world which features remained the proper concern of natural philosophy.
In the remainder of the book, McGrath discusses the gradual division of natural philosophy into philosophy and natural science (chapter 5). Then in chapters 6–10, he goes on to discuss his account of natural philosophy as ‘a way of imagining the natural world that both preserves and integrates its objective and subjective aspects’ (p. 129). The idea being that ‘subjective and objective accounts of the natural world can be woven together, in a comprehensive account of what any individual makes of nature’ (p. 165).
What should one make of all this though? Well it is not Aristotelian. By construing nature as kosmos rather than phusis it is hard to see how one avoids making the subject of natural philosophy bodies qua projectiles. Qualitative considerations are thus excluded from natural philosophy and the only scientific consideration of such bodies will be the measurable changes of their motions. Had science been understood as a type of knowledge (episteme) rather than a method of investigation and nature construed as phusis, then it would be possible to secure a scientific role for natural philosophy through a study of qualitatively distinct physical causes. In the absence of such a study, however, a whole swath of reality is excluded from scientific investigation. Does it really not matter which kinds of things move other things and why? Or what motion is rather than just its quantifiable changes? Or even whether one can reason from knowledge of the natural world to the existence of an unmoved mover? One could go on, but it is still possible to compliment McGrath for trying to reinvigorate natural philosophy even if one disagrees with the character of the reinvigorated discipline set forth.
