The Nature of Human Persons

Metaphysics and Bioethics

Jason T. Eberl

• Verlag: University of Notre Dame Press
• Jahr: 2020
• ISBN:
  9780268107758
• Thema: Philosophy
• Thema: Ethics & Moral Philosophy

For a human being to exist, does it require an immaterial mind, a physical body, a functioning brain, a soul?

Is there a shared nature common to all human beings? What essential qualities might define this nature? These questions are among the most widely discussed topics in the history of philosophy and remain subjects of perennial interest and controversy. The Nature of Human Persons offers a metaphysical investigation of the composition of the human essence.

Jason Eberl also considers the criterion of identity for a developing human being—that is, what is required for a human being to continue existing as a person despite undergoing physical and psychological changes over time? Eberl places Thomas Aquinas's account of human nature into direct comparison with several prominent contemporary theories: substance dualism, emergentism, animalism, constitutionalism, four-dimensionalism, and embodied mind theory. These theories inform conclusions regarding when human beings first come into existence (at conception, during gestation, or after birth), how we ought to define death for human beings, and whether (and if so how) human beings may survive death. Ultimately, The Nature of Human Persons argues that the Thomistic account of human nature addresses the matters of human nature and survival more holistically than other theories and offers a cohesive portrait of one's continued existence from conception through life to death and beyond.

CHAPTER ONE

What Am I?

Questions of Human Nature and Identity

There are myriad approaches from various scholarly disciplines to respond to the fundamental question of human nature “What am I?” Psychologists probe the contents of the conscious and subconscious mind to help individuals understand their authentic self. Sociologists observe how human beings behave collectively to determine if there are any informative generalizations that may be drawn. Anthropologists and biologists are concerned with how human beings have culturally and physically evolved over eons of time. Theologians of different religious traditions seek to define and justify certain beliefs about humanity’s place in the universe—whether, for example, each of us exists as a special creation in the “image and likeness of God” (imago Dei) or is merely a drop in the cosmic ocean of being with no individual essence. Ethicists debate the moral status of human beings at various stages of life and what specific rights and duties are applicable to, for example, embryos, fetuses, infants, children, cognitively disabled adults, irreversibly comatose patients, and the deceased. Finally, metaphysicians investigate, among others, the following interrelated questions: “What composes a human being?”¹ or “With what is a human being identical?” and “What accounts for a human being’s persistence through time and change?” The first pair of questions is concerned with determining what material or immaterial substance or set of parts is necessary in order for a human being to exist—for example, a living body of the species Homo sapiens, a functioning human (or human-like) brain, a mind distinct from one’s body and brain, or a nonphysical soul somehow related to one’s physical body. The last question pertains to what is necessary for one to continue existing as the numerically same human being despite physical and psychological changes we inevitably experience.

These questions regarding the ontology of human beings have been a central concern throughout the history of philosophy, with multiple accounts having emerged of what constitutes the essence of human nature—an area of inquiry sometimes termed “philosophical anthropology.” The term essence refers to the set of specific parts, properties, capacities, et cetera that are shared by all and only human beings. This is not to say that nonhuman entities may not also possess some of these essential human features, but possessing the entire set—whatever the set comprises—is both necessary and sufficient for one to count as a human being.

In the West, the Greek philosophers Plato and Aristotle offered distinct views of what a human being fundamentally is. For Plato, a human being is identical to an immaterial soul—construed equivalently to what we would today call a “mind”—that is “imprisoned” for a time in a material body before death sets it free, either to be united with another body or to spend eternity contemplating the source of being, truth, and goodness.² Aristotle conceived of a human being as a composite unity of an immaterial soul and a material body of which the soul is the formal principle—a view known as hylomorphism.³ This basic controversy regarding a human being’s relationship to her material body has continued to drive debate among philosophers throughout the ensuing centuries into the present day. Numerous accounts have been proffered identifying the human essence as an immaterial soul or mind, a living animal body, a functioning brain, or a bundle of psychological states, to cite some of the principal views. Depending on which of these theses one favors, the criterion of a human being’s identity through time and change consists in sameness of soul or mind, continuity of biological life processes, continuity of neural functions, or some form of psychological continuity involving memory, personality traits, or self-consciousness.

In contemporary analytic philosophy, the methodological school of thought in which the present investigation is situated, the debate between philosophers who reduce human nature to either its physical or psychological properties, those who hold that human nature includes both types of properties, and those who argue that human nature transcends such properties has focused on three distinct camps. Substance dualists maintain a contemporary version of Plato’s view that a human being is identical to an immaterial soul that is conjoined to a material body during one’s earthly life. Reductive materialists contend that human nature is nothing “over and above” the biological and neurophysiological facts that are subject to empirical scientific investigation: all the physical and psychological states of a human being can be wholly explained in virtue of the physical properties had by one’s body. Finally, nonreductive materialists take seriously the data provided by empirical science, while nevertheless maintaining that there are some aspects of human nature that cannot be wholly explained in terms of physical properties alone. The nonreductive thesis is not intended to imply that human nature includes an immaterial component that essentially exists with absolutely no reference to a physical body, as substance dualists claim. Rather, the thesis is that some states of a human being—namely, certain types of psychological states—cannot be explanatorily reduced to states of one’s physical body, such as neurons firing in the cerebrum; rather, a further psychological explanation is required.

An Alternate Via Media

This volume will present Thomas Aquinas’s Aristotelian-influenced hylomorphic view of human nature as a “middle way” between the extremes of substance dualism and reductive materialism that also avoids certain issues that arise for other nonreductive accounts. Though Aquinas lived and wrote in the thirteenth century, scholars continue to find merit and relevance in his ideas. Several distinct movements of “Thomism” throughout the twentieth century bear witness to Aquinas’s enduring influence in both philosophy and theology.⁴ Most recently, an emerging area of scholarship has sought to place Aquinas’s views in fruitful dialogue with those of contemporary analytic philosophers on a variety of topics.⁵ Although this approach risks reading Aquinas ahistorically—that is, without paying due attention to the historical context in which Aquinas situates his arguments, as well as the concepts and terminology he utilizes—I will endeavor to remain faithful—particularly in the reconstruction of Aquinas’s account of human nature in chapter 2—to Aquinas’s texts and to offer justifications throughout for how the Thomistic account, far from being an anachronism of merely historical interest, may be effectively reformulated in contemporary philosophical terms for the sake of fruitful comparative analysis with other contemporary accounts.

In this endeavor, I will be following other recent efforts to accomplish an analytic reconstruction of Thomistic hylomorphism in the areas of philosophical anthropology and the philosophy of mind by, among others, Eleonore Stump, John Haldane, Robert Pasnau, Anthony Kenny, Brian Leftow, David Oderberg, and Jeffrey Brower.⁶ In chapter 2, I will provide a reconstruction of Thomistic hylomorphism utilizing analytic terminology I contend to be congruent with Aquinas’s original conceptual terminology. In chapters 3 and 4, I will compare this reconstructed Thomistic account to several contemporary views representing the three camps described above. It is notoriously difficult to classify Thomistic hylomorphism among the traditional categories of dualism and materialism, for it clearly is neither without qualification.⁷ As will be discussed in chapter 3, Aquinas explicitly denounces Plato’s substance dualist construal of human nature, in which a human being is identified with her soul alone—that is, I = a soul. Yet in chapter 7 I will show how Aquinas understands a human being to be capable of existing after her body’s death, composed of her soul alone—that is, I exist by virtue of my soul but I ≠ my soul; the crucial distinction between the relations of “identity” and “composition” will be explicated in the ensuing discussion. Aquinas’s claim that a human being can survive her body’s death clearly sets him apart from any reductive materialist view of human nature, which identifies a human being with her physical body—that is, I = a body.⁸ Nevertheless, as explicated in chapter 4, Aquinas contends that a human being is essentially an animal—that is, I = a human animal. Attempting to reconcile the various claims Aquinas makes about human nature and to classify taxonomically his hylomorphic view in more readily familiar terms can lead to seemingly outrageous paradoxical statements, as when Lynne Baker states, “Thomistic animalists are substance dualists.”⁹

An emergent consensus is that, depending upon how certain claims Aquinas holds are stressed, Thomistic hylomorphism can be construed either as a type of dualism, as a type of materialism, or as utterly incoherent. The primary aim of the present volume is to provide a coherent reconstruction of Thomistic hylomorphism in contemporary terms that is conceptually faithful to Aquinas’s historically contextualized account and to show how it differs from certain contemporary forms of dualism and materialism. Whether this means that Aquinas should be understood as offering a distinct type of dualism, a distinct type of materialism, or a completely unique alternative will depend on what each reader understands to be the essential premises defining “dualism” and “materialism.” In order to elucidate the nuances of Thomistic hylomorphism, however one further labels it, as well as to demonstrate its advantages as an account of human nature, I will compare it to alternative dualist and materialist views with which hylomorphism has both affinities and differences. In the process, I will derive a set of desiderata that I contend any satisfactory theory of human nature ought to fulfill and will show how, while each of the other theories discussed fulfills some of them, Thomistic hylomorphism satisfies them all.

Desiderata for an Account of Human Nature: An Initial Sketch

The following is a list of nine desiderata I contend ought to be satisfied by any account of human nature, along with a brief justification for the value of satisfying each one. More complete justifications will be forthcoming as each arises within the context of the various theories discussed throughout the volume, and a Summative Excursus following chapter 4 will evaluate how completely each theory satisfies them.

The first desideratum is that it is possible for human beings to survive bodily death. Such survival can take different forms—such as reincarnation, resurrection, or pure spiritual existence.¹⁰ It is important to note that merely the possibility of postmortem survival is countenanced by this desideratum, not the demonstrability thereof. I consider this a desideratum for any account of human nature insofar as it is a fundamental belief held by a significant percentage of human beings cross-culturally. Thus I assert that an account of human nature that takes this belief seriously, and can account for its metaphysical possibility, will be stronger for it, whereas accounts that close off this possibility bear a significant burden of proof for why postmortem survival is not merely false but impossible.

The second desideratum is the acknowledgment that human beings are biological organisms.¹¹ This desideratum is derived from several factors: (a) an evolutionary understanding of how the present human form has developed and the insights that such an understanding provides to inform an overall anthropological understanding of human nature; (b) the clear evidence of correlation between a human being’s mental states and neural states of her brain, which does not entail reduction or identification of the former with the latter but which nevertheless affirms a close relationship of some sort between them; and (c) each human being’s phenomenal experience of her own embodiment.¹² As René Descartes testifies after establishing, following his initial skepticism, that he may trust what he “clearly and distinctly” perceives,

There is nothing that my own nature teaches me more vividly than that I have a body, and that when I feel pain there is something wrong with the body, and that when I am hungry or thirsty the body needs food and drink, and so on. So I should not doubt that there is some truth in this. Nature also teaches me, by these sensations of pain, hunger, thirst and so on, that I am not merely present in my body as a sailor is present in a ship,¹³ but that I am very closely joined and, as it were, intermingled with it, so that I and the body form a unit.¹⁴

The third desideratum, building on the second, is that the physical aspect of human nature is not defined in terms of the existence and persistence of material constituents alone but includes the proper organization and functioning of those constituents in a unified organism. This desideratum involves a rejection of mereological essentialism: the thesis that any whole—including living organisms and a fortiori human beings—has all of its parts essentially, meaning that even the slightest micro-level change will result, strictly speaking, in a nonidentical being coming into existence.¹⁵ There are myriad defenses, going back to John Locke in the seventeenth century and—as I will show in chapter 2—Aquinas in the thirteenth century, of how physical continuity, and thereby numerical identity, of a living organism may be preserved through time and change of its material constituents.¹⁶ After describing how plants and animals may persist through time despite changes in their material constituents, Locke seminally concludes, “This also shews wherein the Identity of the same Man consists; viz. in nothing but a participation of the same continued Life, by constantly fleeting Particles of Matter, in succession vitally united to the same organized Body.”¹⁷

The fourth desideratum involves acknowledging that conscious thought processes—of at least a certain type—are explanatorily irreducible to neural functioning. There is a long history of debate concerning whether mental states—or at least certain types of mental states—are explanatorily reducible to neural states of one’s brain. The claim that mental states are explanatorily reducible means that the existence and nature of such states may be completely accounted for in physical terms alone, to the point where perhaps we should even eliminate “folk psychological” terms—such as belief, desire, and thought—from our philosophical vocabulary.¹⁸ While it might seem that a denial of explanatory reductionism entails a dualistic account of human nature, this conclusion does not follow insofar as there are attempts at nonreductive physicalist accounts of the mind along with a version of dualism known as property dualism, which holds that human beings are physical substances whose brains may generate nonphysical mental properties.¹⁹ Reductivists or eliminativists contend that there is a presumption in favor of their respective views insofar as they do not postulate ontological entities—whether substances, properties, or even linguistic concepts—beyond what is necessary to explain mental phenomena, which is an application of Ockham’s Razor—see the seventh desideratum. Though I do not have space to outline these arguments in detail, I contend that there is sufficient ...

Inhaltsverzeichnis

• Title
• Copyrights
• Dedication
• Contents
• Foreword by Christopher Kaczor
• Preface
• Acknowledgments
• 1. What Am I? Questions of Human Nature and Identity
• 2. This Is Us: A Hylomorphic View of Human Nature
• 3. I Think, Therefore . . . : Varieties of Dualism
• 4. Thou Art Dust: Varieties of Materialism
• 5. Starting Out: The Beginning of Human Persons
• 6. End of Line: The Death of Human Persons
• 7. Is This All That I Am? Postmortem Persons
• 8. Who Is My Sister or Brother? Treating Persons Ethically
• List of Aquinas’s Works and Abbreviations
• Notes
• Bibliography
• Index