Introduction
The question of whether rationality or animal materiality is the defining characteristic of the human race has waxed and waned throughout the long Western philosophical tradition. From the dawn of Christianity until the end of the middle ages, it was generally accepted that man's ability to act rationally was somehow compromised by the occurrence of an original, primal sin. During the Renaissance of the sixteenth century however, Italian thinkers rediscovered classical Greek and Roman learning and began to construct a glorious vision of ‘man’ that contrasted noticeably with the struggling, sinful pilgrim portrayed in the writings of clerical philosophers and theologians. The ‘man’ discovered by Renaissance philosophers was Adam as he might have been before the Fall, “whole and perfect”.Footnote 1 The scientific discoveries of the seventeenth century strengthened Renaissance humanism with the belief that human nature is set on an unswerving course of upward development. The rise of science also led to a belief in human rationality and independence. Human reason was capable of understanding nature and of solving problems that had hitherto been considered insoluble without recourse to God. This burgeoning belief in human rationality and progress exploded in the eighteenth century into the intellectual movement known as “the Enlightenment”, a movement of such powerful impact that it led to the American and French Revolutions.Footnote 2 Enlightenment philosophy, literature and politics were concerned with the equality, dignity and rights of the individual. Thinkers such as Voltaire, Montesquieu, Diderot, Condorcet, Rousseau, Franklin and Bentham among many others argued that all individuals were to be considered equal, because all are equally human in their capacity to be rational. The democracies of the West are founded on Enlightenment philosophical liberalism,Footnote 3 a philosophy of undoubted greatness, but one that tends to glorify the uniquely human capacity for reason at the expense of human materiality. Influenced by Descartes, liberal theorists assume that rationality is an exclusively mental capacity. They believe that the human mind and the human body are different from one another, irreducible to one another and connected only contingently. Moreover, rationality is the “essential” human characteristic, while the body is “accidental”, not a part of the human essence.Footnote 4 This metaphysical dualism leads to a normative dualism in Western societies in which, for example, occupations requiring “mental” labour are perceived as superior to those requiring mainly physical labour. The normative dualism of liberal philosophy also gives rise to a political solipsism. This is the assumption that human beings, with their sealed off “minds”, are self‐sufficient, solitary agents whose interests are separate and often in conflict. Liberal social policies are accordingly directed at minimising conflict rather than fostering cooperation.Footnote 5 Most significant of all, perhaps, is the liberal belief that humans are motivated by the desire for almost unlimited acquisition and that this desire is both rational and moral.Footnote 6
However, Enlightenment notions of the unconditional rationality of man have been under sustained attack since the nineteenth century publication of Charles Darwin's On The Origin Of Species.Footnote 7 This work, together with contemporary research based on Darwin's theory of evolution by natural selection, suggests that the human race is driven by aggressive animal instincts. The nightmarish events of the twentieth century appear to give credence to this viewpoint: as one commentator puts it
The barbarous history of the 20th century – two world wars, the Holocaust and ethnic cleansing – has left many people disillusioned about what it means to be human. Every impression that man makes upon the world seems to be for the worse. The attempt to master nature has led to global warming and species depletion. The attempt to master society has led to Auschwitz and the Gulags. The result has been a growth of anti‐humanism, of despair about human capacities, a view of human reason as a force for destruction rather than betterment.Footnote 8
The combined effects of evolutionary insights into human behaviour and recent historical events herald a looming crisis in Western metaphysics, with the battlelines already drawn between those who accept the somewhat fatalistic Darwinian account of human nature, and their opponents who hold to the Enlightenment view that human rationality is stronger than human instinct. In this paper I will argue that St. Thomas Aquinas’ three‐level description of human nature can resolve the contemporary metaphysical dilemma brought about by the clash of evolutionary theory with Enlightenment humanism. It will first be necessary, however, to undertake a brief review of the background to Darwin's establishment of the doctrine of evolution.
Darwin and the Neo‐Darwinists
By the time Darwin set off upon his epic Beagle voyage in 1831, the Enlightenment notion that it is the essence of man to be rational, and that our animal materiality is accidental, had come to predominate in Western thought. The conviction that humanity is sharply distinguished from the rest of the animal world goes back to Aristotle. However, from the time that Darwin became an evolutionist, he considered man to be an animal on a par with other animals. The doctrine of evolution, which held that different forms of life had developed gradually from a common ancestry, became current in the eighteenth century mainly through the writings of Erasmus Darwin and Jean Baptiste de Lamarck. However, it was Charles Darwin, grandson of Erasmus, who eventually provided the mass of evidence that made the doctrine credible. In so doing, Darwin simultaneously provided proofs of the animal nature of humankind.
The theory of evolution did not, for a long time, appear to contradict the main principles of Enlightenment thinking. On the contrary, the notion of evolutionary progress appeared to reinforce these principles, and was subsumed into the general air of optimism that emanated from the secular vision of the Enlightenment.Footnote 9 However, twentieth century developments of Darwin's original theory by his neo‐Darwinist successors pose a major threat to Western philosophical notions of human rationality and progress. Scientific evidence now indicates that man is driven primarily by instinct. Man may indeed be a rational animal; it seems, however, that he is more animal than rational. Darwinian theory asserts that the evolutionary mechanism of natural selection has strengthened human survival and reproductive instincts at the expense of human rational powers; human nature does not progress morally, but maintains a state of dynamic equilibrium in which aggressive and altruistic instincts are balanced at a stable rate. Thousands of years of human civilisation and culture, it seems, have not succeeded in separating human biology from human morality. Indeed, the whole idea of evolutionary ‘progress’ has now been discredited scientifically:
The human species is by no means the pinnacle of evolution. Evolution has no pinnacle and there is no such thing as evolutionary progress. Natural selection is simply the process by which life‐forms [adapt] to suit the myriad opportunities afforded by the physical environment and by other life‐forms.Footnote 10
Those humans who over vast evolutionary timespans have adapted best physically, intellectually and psychologically to living with their own species, other species and the environment have, through the evolutionary mechanism of natural selection, passed on their genes and shaped the evolution of humanity. However, evolutionary biologists are quick to point out that adaptive success does not equate to moral progress. Adaptive success can be transient and insignificant on an evolutionary timescale. It is no guarantee of the long‐term stability of a species. It may, in fact, be its technological success that ultimately drives the human species to extinction. Progress in science and technology notwithstanding, there has been no fundamental change in the human condition. Our “caves” are more comfortable and our food more easily accessible. We no longer have to physically hunt it down. The “tools” and “language” that make us the most ecologically successful species on the planet have simply become more sophisticated. Technology has upgraded our tools, and our language has become globalised by means of electronic communication. The “global village” does not, however, appear to have added any greater depth or honesty to human communication. A small fraction of the world's population has become healthier and more prosperous; meanwhile the threat of destruction looms over all. Pope John Paul 11 himself has remarked on the “futility” of 20th century progress in his encyclical Redemptor Hominis:
In Jesus Christ the visible world which God created for man (c.f. Gen. 1: 26–30)– the world that, when sin entered, “was subjected to futility”(Rom 8:20; c.f. 19–22; GS 213)– recovers again its original link with the divine source of Wisdom and love … Are we of the twentieth Century not convinced of the overpoweringly eloquent words of the Apostle of the Gentiles concerning the “creation (that) has been groaning in travail together until now”(Rom 8:22) and “waits with eager longing for the revelation of the sons of God?(Rom 8:19), the creation that “was subjected to futility”? Does not the previously unknown immense progress – which has taken place especially in this century – in the field of man's dominion over the world itself reveal to a previously unknown degree that “subjection to futility”? It is enough to recall certain phenomena, such as the threat of pollution of the natural environment in areas of rapid industrialisation, or the armed conflicts continually breaking out with growing intensity, or the power, already present, of self‐destruction through the use of atomic, hydrogen, neutron and similar weapons.Footnote 11
In spite of its resonance with human existence in the twentieth and twenty‐first centuries, however, the deterministic pessimism of Darwinist and neo‐Darwinist theory has aroused antagonism among many scholars. The balance of academic thought is still perhaps tilted towards Enlightenment optimism concerning the nature of man, although the challenge from Darwinism is continuing to grow.Footnote 12 The contemporary philosophical impasse was in fact set in motion in the late nineteenth and early twentieth centuries, when the philosophers Sigmund Freud and Friedrich Nietzsche – well ahead of their time – grasped the nihilistic implications of Darwinism. The latter thinkers both believed that the strength of human animal instincts would forever defeat the efforts of civilisation to transcend them.Footnote 13 Their philosophical speculations contrast sharply with those of Marx and Hegel, both of whom took a progressive view of evolution and both of whom were strongly influenced by Enlightenment optimism.Footnote 14 Although Darwin had proven the fact of evolution, Germanic evolutionary theory in the nineteenth century was more influenced by philosophical idealism than by Darwin's hypothesis that the main mechanism of evolution is natural selection. Natural selection propels evolution through a mixture of chance and design. German biologists, on the other hand, saw all species as modifications of a basic archetypal form,Footnote 15 an indication that nature is built to a rational plan, and not a product of the random variability upon which natural selection operates.Footnote 16 Both Marx and Hegel believed that human evolution is driven primarily by human rationality, and that the moral and social progress of humanity is guaranteed to progress in dialectical stages.Footnote 17 These two views of evolution have conflicted and overlapped ever since Darwin formulated his theory, although Darwin's theory is now pre‐eminent in scientific circles.Footnote 18 The Marxist‐Hegelian philosophical perspective on human nature continues however to be highly influential in academia. It has affected theological as well as philosophical speculation, particularly in relation to natural law theory and the doctrine of original sin, topics I will return to at a later stage of the discussion. At this point however we must turn to the thought of Thomas Aquinas, whose theory of human nature holds the key to resolving the present philosophical dispute.
Aquinas and Human Nature
It is an interesting fact that, back in the thirteenth century, St. Thomas Aquinas faced a similar philosophical dilemma to the one which now obtains as he formulated a theory of human nature upon which to base the norms of the natural law. By then, the complexity and variety of the natural law tradition “demanded a synthesis of genius”.Footnote 19 This synthesis was achieved by Aquinas, though his account of human nature fell out of favour from the Renaissance onwards.
Two strains of tradition dominated the diverse strands of natural law interpretation in the mid‐thirteenth century. The first, termed ‘the order of nature’, is associated with Greek philosophy and with the Roman jurist Ulpian. It emphasised the given physical and biological structures of nature as the ground of morality. Ulpian defined the natural law as “what nature has taught all animals”.Footnote 20 The natural law is thus not peculiar to the human race but is the generic rule of action common to humans and to animals. Ulpian's sense of the natural law identifies it with animal instinct, and is echoed by the Darwinian account of human nature. The second, ‘the order of reason’, comes primarily from the Romans, although Aristotle was also associated with this strand of natural law thinking. Cicero spoke of the natural law as the innate capacity of reason to direct action towards the human good.Footnote 21 The Roman view of human nature as unconditionally rational is echoed in the powerful Enlightenment emphasis on human rationality. Aquinas succeeded in incorporating both ‘the order of nature’ and ‘the order of reason’ into his theory of human nature, which he defines as follows:
The order in which commands of the law of nature are ranged corresponds to that of our natural tendencies. Here there are three stages. There is in man, first, a tendency towards the good of the nature he has in common with all substances; each has an appetite to preserve its own natural being. Natural law here plays a corresponding part, and is engaged at this stage to maintain and defend the elementary requirements of human life. Secondly, there is in man a bent towards things which accord with his nature considered more specifically, that is in terms of what he has in common with other animals; correspondingly those matters are to be of natural law which nature teaches all animals, for instance the coupling of male and female, the bringing up of the young and so forth. Thirdly there is in man an appetite for the good of his nature as rational, and this is proper to him, for instance, that he should know truths about God and about living in society. Correspondingly whatever this involves is a matter of natural law, for instance that a man should shun ignorance, not offend others with whom he ought to be in civility, and other such related requirements. While single in itself, the reason has to direct all the many matters affecting human life; consequently all that can be controlled fall under the law of reason.Footnote 22
In applying Aquinas’ solution to a philosophical problem that has recurred eight centuries later, one cannot but be impressed by his prescience in categorising the human person on the three levels of substance, animal and rational animal. It is, after all, only forty years since the code contained in DNA was deciphered. This enabled geneticists to discover, among other things, that humans share ninety‐eight per cent of their genes with chimpanzees and thirty‐five per cent with daffodils. They have also found out that humans share certain patterns of behaviour with other animals as a result of their common subjection to evolutionary forces. Contemporary scientific research vindicates Aquinas’ insistence that man's bodily materiality is part of his essence.
The first two levels of Aquinas’ theory correspond exactly to the Darwinian account of human nature: Darwin identified the survival and reproductive instincts as the driving forces of human existence. It is these instincts that are implicated in disproportionate desires for material goods and sensual pleasures, and, according to the neo‐Darwinists, prevent human nature from progressing morally. However, Aquinas also stresses that the third component of human nature – rationality – is its most important and defining feature. In this way, the deterministic pessimism of Darwinian theory is avoided. Aquinas however does not advocate the kind of unconditional human rationality that is claimed by Enlightenment philosophy, and it is in his balancing of the animal with the rational in man that he provides a clear solution to the metaphysical dilemma confronting Western philosophy today.
The Problem of Evil
Aquinas would agree, up to a point, with the Darwinian emphasis on the power of instinct, if not wholly with the reasons Darwin gives in explanation. Aquinas argued that due to the loss of the grace of original justice, a consequence of original sin, human nature is deprived of the integrating principle it was destined to have. As a result of this deprivation “all the powers of the soul are in a sense lacking the order proper to them”Footnote 23 and nature is infected with the wounds of ignorance, malice, weakness and intemperance.Footnote 24 These wounds have strengthened the human race's most basic instincts at the expense of its rationality. Due to original sin, mankind is capable of using its rational powers in the service of instincts whereas, according to Aquinas, it should always be the other way around: “ … man, when perfected by virtue, is the best of animals, but when separated from law and justice he is the worst. For he can use the weapons of reason, which other animals do not possess, to satisfy his lusts and brutalities”.Footnote 25 Aquinas also identifies in particular “a law of lust” which is a penalty of original sin:
Now by divine ordinance there is a law apportioned to man in accordance with his rightful condition, namely that he should act according to reason. So valid was this law in his original state that nothing non‐reasonable nor unreasonable could then take him unawares. But when he turned from God he fell into a condition where he could be carried away by sensuality. This befalls each particular individual to the extent that he falls from reason: in effect he becomes like the beasts who are borne along by their sense appetites … Footnote 26
According to Aquinas, before original sin mankind was indeed unconditionally rational; after original sin however, human beings are only potentially rational. Strengthened by the effects of this primal sin, our animal instincts all too often drive us to gravely irrational behaviour. This weakness in human rationality is identified by Aquinas as the pivot upon which human good and evil oscillate.
As we have seen, the notion of an original sin fell out of favour philosophically from the Renaissance onwards. However, St. Thomas’ incorporation of this concept into his theory of human nature enables it to reconcile Darwinian evidence of the power of instinct with Enlightenment views on rationality, while avoiding the pessimism of the former and the excessive optimism of the latter. Despite original sin, the human race remains capable, through the power of grace, of attaining the rationality that should define its nature. Significantly, it would seem that the metaphysical dilemma confronting contemporary philosophy can only be resolved by reintroducing the notion of a primal sin. If this were to happen, a further fertile field of inquiry would then be opened up: since Darwin asserts that the evolutionary process is implicated in the strengthening of the survival and sexual instincts, it could be argued that a primal sin, occurring at the outset of human history, somehow affected the course of evolution itself. Indeed, given what is now known about the role of evolution in shaping human behaviour, it seems self‐evident that an ‘original sin’ would have impacted upon the subsequent operation of evolutionary forces. An exploration of this interesting possibility is, however, outside the scope of this paper.
The Question of Progress
If, as I have argued, the Thomistic theory of human nature resolves the opposing Marxist‐Hegelian and Darwinian perspectives, where does that leave the issue of human moral and social progress? The Marxist‐Hegelian view of evolution, no longer accepted in reputable scientific circles, has cast doubt – even among theologians – both upon the doctrine of original sin and the related natural law theory.Footnote 27 If, as Marxist‐Hegelianism claims, human nature progresses morally in an inevitable upward direction, how can there have been a primal ‘fall’? By the same token, if human nature is in a constant state of flux, how can anyone subscribe to a natural law theory which asserts that nature to be universal and timeless? I have suggested that the ultimate triumph of Darwinian evolutionary theory promises to renew philosophical interest in the doctrine of original sin. Significantly, it also casts Thomistic natural law theory in a new light.
In recent decades, it has become fashionable in moral theology to criticise the idea that universal moral norms can be abstracted from an unchanging human nature. St. Thomas's natural law theory is often criticised for being “timebound” and “static”. In light of the pessimism of the neo‐Darwinist argument that human nature has remained fundamentally the same since the first appearance of Homo sapiens over one hundred thousand years ago, Aquinas’ theory appears striking in the possibilities it allows for human morality. In a Darwinian context, Thomistic theory in fact points the way towards limitless human moral and social progress, since it suggests that each and every human being can, in fact, fulfil his or her potential for rationality.
At this point, rationality in the Thomistic sense must be distinguished from the instrumentalist, disembodied notion of rationality that came to the fore with the rise of science and Cartesian philosophy. Aquinas’ notion of rationality includes the dimensions of instrumentality and logic, but is much richer than this. ‘Reason’ in the Thomistic sense of recta ratio“entails the totality of the human tendency to want to know the whole of reality and come to the truth. This sense of reason includes observation and research, intuition, affection, common sense, and an aesthetic sense in an effort to know human reality in all its aspects”.Footnote 28 For Aquinas, the rational faculties direct and coordinate emotion and instinct but are not separate from them. Reason should never be put in the service of instinct, but reason should be informed by emotion and instinct. According to Aquinas, the more rational we become, the more moral and hence more human we become. To be rational, then, is to be loving in the best of every sense of that word. Further, individual moral and spiritual progress is intimately bound up with social progress, since it is part of man's rational nature that “he should know truths about God and about living in society … [and] should shun ignorance, not offend others with whom he ought to be in civility, and other such related requirements”.Footnote 29 The quest for true human progress is really the quest for the fullness of human rationality. It is a quest that can bear fruit only when human beings are willing to conform to the laws of their nature. According to the Thomistic view of human nature, for example, and in contradistinction to the Enlightenment perspective, to excessively indulge one's desires for material goods and for sensual pleasures is gravely irrational and against the natural law. The ability to conform to the law of nature is one that cannot, of course, be achieved through unaided human effort, but is dependent upon the gift of grace.
Conclusion
The combination of Enlightenment optimism concerning the nature of man and the now discredited scientific notion of evolutionary progress has, over the last two centuries, profoundly influenced Western culture, philosophy, politics, education and scholarship in general. The resulting belief in the ability of humanity to take charge of its own destiny has generated new academic disciplines collectively termed the ‘social sciences’. Enlightenment thinkers argued that the Christian, biblical view of human nature had been disproved by science, and that man's nature could only be known by the systematic doubt and reliance upon first‐hand experience (as opposed to second‐hand authority and dogma) advocated by philosophers such as Descartes. Scientific methodology would reveal the laws of man's nature and existence in the same way that such procedures had demonstrated that the movement of the planets was governed by gravity. Similarly the way society works can be understood through economic and statistical analysis, and once understood social relations would be perfected through more efficient and rational management.
The establishment of democracy was undoubtedly the greatest achievement of that momentous period in the history of the West. New scientific evidence as well as the events of the twentieth and early twenty‐first centuries have, however, challenged not only Enlightenment beliefs and assumptions concerning the nature of man and society, but also demonstrated the fragility of the democratic system and its many failures. Democracy has not been the all‐purpose panacea that its founders believed it would be. Roy Porter has written that while the Enlightenment “helped to free man from his [oppressed] past … it failed to prevent the construction of new captivities in the future. We are still trying to solve the problems of the modern, urban industrial society to which the Enlightenment was midwife”.Footnote 30 It must also be admitted that the prosperity which fuels Western democracy depends upon the exploitation of vast numbers of the world's poor; neither can it be denied that Enlightenment insistence on the rationality and morality of egoistic desires has contributed to the development of a hedonistic society obsessed with celebrity, success and the acquisition of material wealth. In attempting to both secure the freedoms and advantages brought about by democracy as well as to remedy its many and serious flaws, philosophers must strive to express a clearer vision of the good individual and the good society than heretofore, and consider anew the ideals and principles that should inform education and social organisation. To know how things ought to be, however, requires knowledge of what can be; to know what can be in turn requires a wise and accurate account of what is. More specifically, it requires a deep understanding of human nature with all of its needs, possibilities and motivations. The insights into human nature and behaviour achieved by Darwin and the neo‐Darwinists, when placed within the theological context outlined by Aquinas, have an important contribution to make to our understanding of the problems that confront humanity. I have argued that in Aquinas’ theory of human nature, philosophy has an invaluable resource to draw upon in confronting the contemporary metaphysical challenge caused by the clash of evolutionary theory with Enlightenment humanism. However, this would require an abandonment of the view that man is the sole author of his destiny. It would also require an acceptance of the fact that social progress is dependent upon the spiritual development of the individuals who form communities of every sort.
It is a remarkable fact that Aquinas’ account of human nature can absorb and transcend the Darwinian challenge, while the centuries old tradition of Enlightenment philosophy, a philosophy itself spawned by the rise of science, cannot. Aquinas’ theory was, after all, formulated at a time when the category of empirical scientific knowledge was centuries away from discovery. In its synthetic power, Aquinas’ thought is as relevant today as it ever was, and shines a guiding light forward for Western metaphysics.
