I write a lot about “human flourishing”—living a whole and healthy life marked by “shalom” (complete well-being). Yet to define what true flourishing is for us, we must first define what a human is, for different types of things flourish in different environments.
The tulips planted in my backyard are flourishing because they are planted in the right type of soil, with the right amount of moisture, the right nutrients and the right amount of sunlight. Yet if I dug a hole and “planted” my dog in the backyard with exactly the same conditions, needless to say he would not flourish. Just the opposite—he would die. This is because the nature of a tulip requires one environment to flourish, but the nature of a dog requires a different environment to flourish.
So it is with humans—what type of thing we are determines the type of environment we need to flourish. So what type of thing are we—what is it to be “human”?
There are ultimately three answers to this question. The first is that we are essentially a combination of a material and an immaterial dimension (a combination of a body and a soul). This view is known as “Substance Dualism” and was the historic view until the time of the “Enlightenment” (roughly the 18th century).
The second answer, given by the “Enlightenment,” is that we are fundamentally physical or material beings. We are ultimately a body, or more basically matter in motion. This view is known as “Physicalism.”
The third answer, a bit newer on the scene, is that we are essentially nothing—we have no essence, be it material or immaterial. What we are is what each of us decides we are—each of us can define our nature as we see fit, from person to person and even differently by the same person at different times. This third view may be termed “Postmodern Anti-Essentialism.”
Each of these definitions lead to wildly different conceptions of human flourishing and the common good. Therefore we must think hard and well in order to determine the correct answer. Only then can we determine what type of environment will help us humans flourish. And only then can we answer what we should seek as the common good, in order for all human persons to flourish in these ways.
Over the next eight weeks I’ll discuss these three answers and their implications in some detail. I will also apply these answers to a number of the pressing issues of our day.
Substance Dualism: The Basis of Equality, Dignity and Public Discourse
For much of intellectual history the dominant view has been Substance Dualism—we share a fixed, common human nature (soul, essence, immaterial dimension) in addition to our bodies.
This belief in a shared human nature is the foundation of treating one another equally (“humane” treatment). Since we are all essentially the same, no matter how different we may be in other ways, each person deserves to be treated the same. Furthermore, within the Christian intellectual tradition this essential nature is tied to being created in God’s image (sharing the “imago Dei”), and so each person is to be treated as someone of great worth and value, worthy of our deepest respect.
This leads the society with this view to seek and protect the “common good”—the flourishing of all collectively within the society, no matter how they differ in other ways, based on their shared human nature. This means rejecting attempts to privilege one group or class over others based on differences not grounded in this shared human nature.
For instance, for those of European descent to claim special rights based on this ethnic background is wrong, on this view, for one's ethnicity does not make one more or less human. People of all ethnicities share the very same human nature—all are equally and fully human. Therefore claiming special rights based on this non-universal characteristic is wrong, an leads to societal divisions and oppression of others—the exact opposite of promoting the common good in society.
(Of course, the same can be said of any other sub-groupings in a society, be it religious, gender, sexual orientation, and so on.) The only way a society can promote the common good is to ground rights (and obligations) in our shared humanness, rather than in other identities not shared by all.
From this developed the values of free speech and assembly to foster public discussions about human flourishing and the common good. Only through such public, civil, reasoned discourse is a society able to discuss and mutually discover how best to create the environment most conducive to human flourishing and the common good in light of our shared human nature.
Returning to the illustration of growing tulips, a Tulip Club must first understand the nature of tulips to discuss how they grow best—which elements in the environment will cause tulips to flourish, in light of their nature. In the same way, as there is an understanding of the nature of human persons we can come together and discuss how to create an environment (society) most conducive to human flourishing. In such a discussion all views receive a hearing, and the best view (that which is most supported by fact) is adopted. Only in this way can those in a society come together and have civic, and civil, discourse, resulting in just laws for all and a society that ultimately leads to human flourishing and the common good.
Defining Substance Dualism
With so much at stake, it is important to understand the basic features of this view: “substance” and “dualism.” Let’s start by defining these terms. First, the easier of the two: “dualism.” This implies that we are ultimately two of something. But two of what?
We are ultimately two “substances.” The word “substance” used here is not what we now commonly understand the word to mean. We usually use the word “substance” to mean something physical. But here I am using it technically and philosophically to mean, literally, “that which stands under” (“sub-stands”). Look around and you notice many properties. Examples may be the property of hardness, or kindness, or intelligence, or athleticism or health. Notice these properties are not just floating around, but are properties of something: a mind, a person, a tree, and so on. Substances are those things that “have” properties, that “stand under” these properties, that the properties are “in.”
So technically a substance is something that has properties, but is not “had” by anything more basic. Concerning human persons, we are two substances. We are a material substance (a body). Our bodies have properties including height, weight, location and capacities such as the ability to move in certain ways.
But we are also an immaterial substance (a soul, also known as an individuated human nature). The soul is a deep unity of parts, properties and capacities. We may have the property of being kind, intelligent or courageous. And we have capacities in a number of areas: intellectual, emotional, relational, volitional and spiritual. As we develop these capacities we are said to be maturing (thinking in more mature ways, handling emotions in more mature ways, relating to others in more mature ways, making more mature decisions and maturing in our relationship with God).
So, in sum, Substance Dualism is the view that we are a combination of a soul and a body—a duality of these two substances.
How Do the Soul and Body Relate? Implications for Spiritual Formation and Biomedical Ethics
There are many more technical nuances and distinctions that I’m passing over in this summary of Substance Dualism. For more detail see the books I list in the Philosophical Anthropology section of my Recommended Books. But I do want to make one further, more technical distinction which is very important as it relates to how we grow in Christ (spiritual formation) and issues in biomedical ethics.
There is a long-standing, intermural debate among Substance Dualists as to the relationship between the body and soul—a boxing match of sorts. In one corner, with Plato as the trainer, is Rene Descartes, advancing what is known as “Cartesian Dualism.” On this view the soul is related to the body as water is to a glass. The water is in the glass, but that relationship is very superficial—it doesn’t affect the water or the glass in any way. They go on being what they are regardless of the other. In the same way, for the Cartesian Dualist the fact that the soul is “in” the body and the fact that the body “contains” a soul doesn’t make any difference to either. They keep on being what they are, unaffected by the other.
If this is the nature of the relation between the soul and body, our spiritual formation is purely a spiritual activity—what we do, or don’t do, with our bodies makes no difference at all. We grow only by “spiritual” activities such as prayer and Bible study. Our posture in prayer is irrelevant. The physical space our bodies occupy makes no difference (such as how a church sanctuary is designed). Exercise and nutrition are irrelevant to the health of our souls. Taken to its extreme, sinning “in the body” is not harmful, because that is not where the “spiritual action” is. (This was the view of the Antinomians [literally “no law”], which is related to the Gnosticism and Docetism that sections of the New Testament were written to counter.)
Concerning biomedical ethics, there is much discussion of when life begins and when life ends. This is very hard to determine for the Cartesian Dualist, because the body is a machine that can run whether or not a soul is present. Therefore, the presence or absence of a bodily function tells us nothing about whether the soul is still present.
In the other corner of this boxing ring, with Aristotle as the trainer, is Thomas Aquinas, advancing what is known as “Thomistic Dualism.” On this view the relationship of the soul and body is very deep—what happens in the body affects the soul, and what happens in the soul affects the body.
If this is the nature of the relationship, spiritual formation includes both soul and body. Certainly “spiritual” activities such as prayer and Bible study are important. But so are “physical” practices such as fasting. Such bodily disciplines affect our soul and cause us to grow spiritually. Likewise, the way a sanctuary engages our senses (smell, touch, taste, sight and sounds) will have positive or negative effects on our worship. Exercise and nutrition foster or hinder our spiritual health, along with how well we can think, relate to others and have healthy emotions. For more on how Thomistic Dualism underlies spiritual disciplines see Dallas Willard’s The Spirit of the Disciplines.
For issues in biomedical ethics, if the soul and body have such a deep relationship to one another, questions of life and death are more easily answered. Concerning euthanasia, for instance, on this view the soul’s presence is necessary for the body to function. Therefore, if the body is functioning on its own without life support, then the soul is still present. Conversely, if the only thing sustaining bodily functions is life support, then the soul has already left and the person is no longer alive. For more on this see my and J.P. Moreland’s “Aquinas vs. Locke and Descartes on the Human Person and End-of-Life Ethics.”
As may be evident by what I’ve just said, I think Thomistic Dualism is preferable. It makes sense of why spiritual disciplines help us grow in Christ. It makes sense of us doing poorly on tests when we have not eaten well. It makes sense of us getting ulcers when we worry too much. And it affirms the goodness of the body as part of God’s creation—it is more than, as Plato said, the “prison-house of the soul.”
There are many who reject Substance Dualism. Are there any good reasons to believe it is true, and therefore believe there is a fixed human nature that grounds our equality and dignity? I think there are. In the next two weeks I’ll offer six arguments supporting Substance Dualism.
Until then, grace and peace.
For further reading I suggest Philosophy Made Slightly Less Difficult: A Beginners’ Guide to Life’s Big Questions by Garrett DeWeese and J.P. Moreland, “Substances, Essences and Natures” (pages 41-47).