Can we have a comprehensive view of nature if we do not include an adequate account of consciousness, cognition, and value? Central to the orthodoxy of reductionist materialism is that these features of reality are fully explicable in terms of chemical and physical processes: in some theories they are mere epiphenomena of these processes; in others they are simply dismissed as illusions, shown to be so by the great successes of science.
Even those scientists, especially biologists, who resist a reductionist methodology in which physics becomes the fundamental science, nevertheless embrace an ontological reductionism according to which there is nothing more to reality than material components. Richard Lewontin, a Harvard biologist, has made this point explicitly:
It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter-intuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is absolute, for we cannot allow a Divine Foot in the door.
Notice for Lewontin the choice seems clear: either we accept a materialistic view of the world as a complete account of nature, even if not yet realized, or we must allow some appeal to God to explain the world. In a new book, Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly False, Thomas Nagel, distinguished professor of philosophy and law at New York University, challenges Lewontin's dichotomy. He argues that evolutionary biology aligned with reductionist materialism cannot, in principle, offer an adequate account of what nature is and how living organisms have developed historically to the point that there are conscious, intelligent agents able to distinguish between good and bad, right and wrong.
Nagel, who tells us that he is an atheist, also rejects various forms of theism that appeal to the intentional agency of God to explain the complexities of nature and human nature. The principal focus of his book, as the subtitle indicates, is his criticism of Neo-Darwinian reductionism which, he says, is "incapable of providing an adequate account, either constitutive or historical, of our universe." This reductive materialism purports to capture life and mind through an extension of Neo-Darwinian evolutionary theory. "I find this view," he says, "antecedently unbelievable—a heroic attempt of ideological theory over common sense." The criticism of materialism is not new; less expected is the criticism of the adequacy of evolutionary biology.
Nagel does not find theism to be more credible as an account of the origin and development of life and intelligence. He is interested in possibilities other than Darwin or God, and he champions a view, "naturalistic teleology," which he thinks may provide an account of nature that includes mental faculties as constitutive features.
For Nagel, an adequate understanding of nature must explain: 1) the emergence of living organisms from a lifeless universe; 2) the development of these organisms to greater and greater complexity; 3) the emergence of consciousness among some living things and the central role consciousness plays in their lives; and 4) the development of consciousness "into an instrument of transcendence" that can grasp objective reality and objective value. He begins with consciousness and argues that psychophysical reductionism does not do justice to what are really essential features of our world. Reductionism tries to explain consciousness either by reducing mental concepts to the effects of brain states or, in the case of "eliminative materialism," arguing that mental concepts do not really exist at all.
Nagel appeals to our common sense judgment that human subjectivity is not reducible to physical categories. If we start with a commitment to materialist reductionism, we must reject this common sense judgment. Nagel reverses the argument. He thinks that, starting from the obvious truth of our being conscious agents, inescapable components of reality, we discover an insuperable barrier to psychophysical reductionism.
Moreover, this very reductionism is part of a broader naturalistic view of the world that cannot survive without it. We need an explanation that accounts for the appearance of organisms that are not only physically adapted to the environment but also conscious subjects. Scientific and philosophical theories that rely only on the conclusions of the empirical sciences cannot, in principle, provide an explanation of a natural order that has consciousness and mind as fundamental features. As Nagel remarks, "materialism is incomplete even as a theory of the physical world, since the physical world includes conscious organisms among its most striking occupants." Evolutionary biology explains many things about the development of living beings, but it cannot explain the emergence of evolutionary biology itself.
Moral realism and evaluative judgments (about what is good and bad as objective categories, not merely subjective states) are incompatible with a Darwinian account of evolution’s influence on our faculties for making such judgments. If those faculties are exclusively the result of natural selection, there is no reason to expect that they would lead us to detect "mind-independent moral or evaluative truth." The ability to detect such truth "would make no contribution to reproductive fitness." Rather than reject moral realism in the name of evolutionary materialism, as some do, Nagel again reverses the argument: since there is an objective moral order, an extended evolutionary theory that explains moral judgments in physical terms must be false.
Nagel's arguments that consciousness is not reducible to material phenomena, that there is an objective order of value, and that we do have knowledge of the world are all dialectical. He asks us to recognize, on reflection, their obvious truth. If we accept as a starting point a worldview that has reductive materialism as a first principle, we will not be persuaded by Nagel. One of the benefits of Nagel's book is that he calls into question this first principle and asks us to consider anew an adherence only to material causes.
In examining possible explanations for the origin of life, Nagel thinks that to say the process was the result of chance events or "directionless physical law" challenges credulity. He also rejects what he calls "creationism," the view that the origin and development of living things is the result of specific intentional acts of a divine agent. He thinks that it is properly a scientific project to explain the origin of life and of consciousness. The contemporary natural sciences, however, cannot adequately offer such explanations, and when combined with materialist reductionism make claims that are false.
Nagel opts for another possibility, what he calls "natural teleological laws governing the development of organisms over time." He thinks this "nonpurposive teleology" is different from the other alternatives: "chance, creationism, and directionless physical law." Naturalistic teleology means that there are organizational and developmental principles that are irreducible parts of the natural order, yet "not the result of intentional or purposive influence by anyone." The natural order that is the source of unicellular organisms and eventually of conscious, intelligent agents capable of value judgments has to be different from what is described by materialist reductionism.
To describe this expanded sense of nature, Nagel appeals to a naturalistic teleology according to which there is an immanent directedness in nature, a propensity to give rise to beings like us. Here he cites the inspiration of Aristotle. He notes the strong resistance in the scientific culture to any hint of teleology, since it is commonly thought that modern science was born by rejecting such interpretive strategies. Nagel does not deny the importance of evolution as a description of the vast changes that have occurred over time, nor does he denigrate the role of natural selection. Rather, he thinks that there must also be a "cosmic disposition to the formation of life, consciousness, and the value that is inseparable from them." Nagel notes that he offers this alternative as the best he can now imagine, but "without positive conviction." What he is convinced of, however, is that life, consciousness, and intelligence have not been "formed from scratch by chance plus natural selection." Indeed, his criticism of Neo-Darwinian reductionism is the most compelling part of his analysis.
"Naturalistic teleology" may advance our understanding of the historical development of living things, but it does not help very much in explaining the way things exist in the world. Here Nagel would be aided by Aristotle's broader conception of natural things. To think of nature only in terms of its material components is not to grasp nature in its full sense; for this we would need what Aristotle calls "form." There is more to nature than material components, but the "more" is not a material more. Aristotle is not a dualist; form and matter are not two separate things; they are co-principles of each natural entity. Speaking in terms of form and matter, substance and accident, act and potency allows Aristotle to offer a comprehensive account of nature and change. It also offers him a good way to distinguish between the inanimate and the animate.
Aristotelian natural philosophy can incorporate the many discoveries of the contemporary empirical sciences and offer the new vision for which Nagel is searching. The mind-body problem disappears in the context of Aristotle's understanding of the rational soul as the informing principle of a human being. To speak of intrinsic propensities in nature, as Nagel does in defending naturalistic teleology, only makes sense, I think, if we accept the full Aristotelian account. Surely, as Nagel realizes, any proposal to integrate Aristotelian thought with contemporary science meets at best skepticism, at worst smug dismissal. A defense of the continuing value of Aristotelian natural philosophy requires significant historical and philosophical analysis. Nagel's criticism of materialist reductionism can encourage alternative visions, including the Aristotelian.
Nagel tells us he is unwilling to accept a theistic explanation that, according to him, "interprets [the] intelligibility [of nature] ultimately in terms of intention or purpose—resisting a purely descriptive end point." The kind of theism applied to the study of nature that Nagel rejects is a top-down theism, which starts from the existence of God and seeks to understand the world primarily in terms of God's intention/purpose. Nagel worries that theism attributes the coming into existence of life, consciousness, and reason solely to divine intervention. Such an interventionist hypothesis amounts "to a denial that there is a comprehensive natural order."
For Nagel, a "creationist" explanation of the existence of life is the biological analogue of dualism in the philosophy of mind. "It pushes teleology outside the natural order, into the intention of the creator—working with completely directionless materials whose properties nevertheless underlie both the mental and the physical." He does not think it necessary to appeal to God to support his view that there is an intrinsic directedness to nature and its processes, yet he does note that this view would be consistent with God's creating nature to be that way so long as there is no "further divine intervention." But to affirm that God is the complete cause of all that is and that all of reality is the result of divine intention or purpose does not require the kind of interventionist hypothesis that Nagel rejects.
An account of divine agency in the tradition of Thomas Aquinas would allay some of Nagel's concerns. Aquinas thinks that science begins not from God's intentions, but with an analysis of nature as we discover it. God creates a universe in which creatures, inanimate and animate, have their own particular natures, their own intrinsic principles of characteristic behavior. There is a real, albeit created, self-sufficiency to nature. This is so because God's continuing causal activity, which is necessary for the ongoing existence of whatever is, operates on a radically different level from the kind of causality that creatures exercise. In fact, even to speak of a different level of causality fails to capture the radical otherness of divine agency. It is true, as Nagel suggests, that theism understands the intelligibility of the world ultimately in terms of God's purpose, but this does not require, as he seems to fear, the denial of an intrinsic intelligibility in nature that the natural sciences discover.
Nagel helps us to see the limitations of the natural sciences and the errors of materialistic reductionism. The natural sciences, even expanded to include a kind of naturalistic teleology, do not need to embrace a theistic vision of the world in order to discover truths about nature and human nature. Yet, if one wishes to search for a full understanding of nature—of its very existence and intelligibility—one must enter the domains of metaphysics and theology; one must recognize that it is created and that it requires the continuing creative act of God in order to be. Naturalistic teleology, just like existence itself, calls for a cause that transcends the created order.
William Carroll is the Thomas Aquinas Fellow in Theology and Science at Blackfriars Hall and a member of the Faculty of Theology of the University of Oxford.