sexta-feira, 9 de setembro de 2011

Modern biology and original sin, Part I

by Edward Feser

In Edward Feser

Our friend John Farrell has caused a bit of a stir in the blogosphere with his recent Forbes piece on modern biology and the doctrine of original sin. Citing some remarks by Jerry Coyne, John tells us that he agrees with Coyne’s view that the doctrine is “easily falsified by modern genetics,” according to which “modern humans descended from a group of no fewer than 10,000 individuals” rather than just two individuals. Those who have responded to John’s piece include Michael Liccione, Bill Vallicella (here and here), James Chastek, and Mike Flynn.

Several things puzzle me about John’s article. The first, of course, is why he would take seriously anything Jerry Coyne has to say about theology. (We’ve seen ample evidence that Coyne is an ignoramus on the subject -- some of the relevant links are gathered here.) The second is why John seems to think that the falsification of the doctrine of original sin is something the Catholic Church could “adapt” to. (John’s article focuses on Catholicism.) After all, the doctrine is hardly incidental. It is de fide -- presented as infallible teaching -- and it is absolutely integral to the structure of Catholic theology. If it were wrong, then Catholic theology would be incoherent and the Church’s teaching authority would be undermined. Hence, to give it up would implicitly be to give up Catholicism, not merely “adapt” it to modern science.

In fairness to John, it seems he may have been speaking imprecisely. He says, for example, that Eastern Orthodoxy does not accept the doctrine, which (as Bill Vallicella has pointed out) is not true. What is true is that Eastern Orthodoxy does not agree with the Catholic way of spelling out the doctrine. So, perhaps John would allow that it is not the doctrine of original sin per se that is in his view problematic, but only the Catholic understanding of the doctrine. Still, at least one of the aspects of the doctrine that John apparently objects to -- the claim that there was an original pair of human beings through whom sin entered the world -- is also traditionally taught by Eastern Orthodoxy. And whatever one says about Eastern Orthodox and other non-Catholic approaches to original sin, the point remains that if John were right, Catholicism would be in trouble.

But John is not right, and the third thing that puzzles me about his article is why he seems to think the evidence cited by Coyne is obviously incompatible with the doctrine of original sin. After all, the question of human origins is not a matter to which biological considerations alone are relevant. Metaphysical considerations are at least as important -- indeed, they are more important, as we shall see -- and when they are factored in it can easily be shown that there is no incompatibility between the doctrine of original sin and modern biology. Nor is the biological evidence something that the Church must now scramble to “adapt” herself to in order to salvage the doctrine. In fact the subject is one that was addressed long ago, by (among other theologians) Neo-Scholastic thinkers writing in the era of Pope Pius XII’s Humani Generis, who tended to approach the issue from a broadly Aristotelian-Thomistic (A-T) point of view. (Unlike Coyne, John has knowledge of Scholastic and A-T philosophy and theology, so it is surprising that he does not consider the possibility that the answers to the questions he raises might be found in these writers.)

There are two main issues that have come up in the discussion sparked by John’s article. First, is modern biology consistent with the claim that the human race began with a single pair à la the biblical story of Adam and Eve? Second, is modern biology consistent with the claim that this pair transmitted the stain of original sin to their descendents via propagation rather than mere imitation? The answer to both questions is “Yes.” In this post I will show why this is so in the case of the first question and in a follow-up post I will address the second. What I have to say in this post will overlap to some extent with what Mike Flynn has said in his own excellent reply to John, and with what Kenneth W. Kemp says in his important recent American Catholic Philosophical Quarterly article “Science, Theology, and Monogenesis” (see ACPQ Vol. 85, No. 2 -- the same issue in which my article “Existential Inertia and the Five Ways” appears). But I will approach things in a somewhat different way than either Mike or Kenneth Kemp do.

What is man?

We can begin by asking what a human being is. The traditional A-T answer is, of course, that a human being is a rational animal. We are animals insofar as we have the capacities typical of animality in general -- nutrition, growth, reproduction, sensation, appetite, and locomotion. These are all purely material capacities, all requiring bodily organs for their exercise. We are rational insofar as we possess intellect and will. These are immaterial capacities, and do not directly depend on any bodily organ, although they do depend on such organs indirectly. I have explained the how and why in several places -- most fully in chapter 4 of Aquinas -- and have addressed some of the relevant issues in earlier blog posts, such as this one. I will summarize only the most relevant points here.

What intellect involves, for the A-T tradition, is the ability to grasp abstract concepts (such as the concept man or the concept being mortal), to put them together into complete thoughts (such as the thought that all men are mortal), and to reason from one thought to another in accordance with the laws of logic (as when we infer from All men are mortal and Socrates is a man to Socrates is mortal). All of this differs in kind, and not just in degree, from the operations of sensation and imagination, which we share with non-human animals. Concepts have a universality and determinateness that no sensation or mental image can have even in principle. The concept triangularity, for example, has a universality that even the most general mental image of a triangle cannot have, and an unambiguous or determinate content that the auditory or visual image of the English word “triangle” (whose meaning is entirely conventional) cannot have. Indeed, concepts have a universality and determinacy that nothing material can have. So while the A-T tradition holds, in common with materialism and against some forms of dualism, that sensation and imagination have a material basis, it also holds that intellectual activity -- grasping concepts, putting them together into judgments, and reasoning from one judgment to another -- is necessarily immaterial. (Again, I’m not defending these claims here but just summarizing -- I’ve defended them elsewhere.)

All the same, for A-T the intellect does depend on matter in an indirect way. For one thing, though the concepts we grasp are immaterial, we must abstract them from the mental images that derive ultimately from sensation, and imagination and sensation are material. For another thing, even when we grasp an abstract concept, we always do so in conjunction with mental imagery (which is why the philosophically unsophisticated often confuse concepts with mental images). For instance, the concept triangularity is not identical with either the word “triangle” (since people who have never heard this English word still have the concept of triangularity) or with any particular mental image of a triangle (since any such image will have features -- a certain color, say, or being scalene -- that do not apply to all triangles in the way that the concept does). Still, we cannot entertain the concept of triangularity without at the same time forming a mental image of some sort or other, whether a visual image of some particular triangle, a visual or auditory image of the word “triangle” or of the corresponding word in some other language, or what have you. The judgment that snow is white is not identical with a visual or auditory image of the English sentence “Snow is white,” since a German speaker (say) could make exactly the same judgment even though he would express it instead with the sentence “Schnee ist weiss.” Still, we cannot form that judgment without at the same time forming some image or other (e.g. a visual or auditory image of “Snow is white,” or of “Schnee ist weiss,” or of some parallel sentence of some other language). And so forth. And this entails that any rational animal must have a material nature that is complex enough to support sensory and imaginative activity of the level of sophistication required to subserve immaterial intellectual activity. Such sensory and imaginative activity cannot be a sufficient condition for intellectual activity, but it is a necessary condition.

Now for A-T, all material things are composites of form and matter, and “soul” is a technical term for the form of a living thing, specifically. The soul is that which organizes a living thing’s matter in such a way that it is capable of the operations distinctive of living things. Since the activities of living things other than human beings are entirely dependent on matter, their souls are themselves dependent on matter, and A-T allows that such souls may therefore have material origins. But the human soul is different, precisely because it is that which makes us capable not only of material activities like digestion and sensation, but also of immaterial activities like thinking. Hence it operates, at least in part, apart from matter. Indeed, unlike the forms of other material things it is a subsistent form, capable of carrying on in existence beyond the death of the body of which it is the form, as a kind of incomplete substance. For this reason, for A-T the human soul cannot in principle have a material origin. In fact, it has to be directly created by God whenever a new human being comes into existence.

On the one hand, then, A-T philosophers and theologians have been open to the possibility of evolutionary explanations of various biological phenomena, including the human body. It might be that sensory and imaginative capacities of a level of complexity necessary to subserve intellectual activity arose gradually via evolutionary processes. On the other hand, there are metaphysical constraints on evolutionary explanations, just as there are on all forms of empirical inquiry. I have discussed some of these constraints in an earlier post, and for a more detailed treatment interested readers might look at an older Scholastic work like Henry Koren’s An Introduction to the Philosophy of Animate Nature, or the biology-related material in David Oderberg’s recent book Real Essentialism. Most relevant to the issue at hand, for A-T there can in principle be no evolutionary explanation of the human soul precisely because the human soul can have no material cause of any sort. We know this because (so A-T holds) we know on independent grounds that the distinctive capacities of the human soul (intellect and will) cannot be material.

A useful analogy is provided by the famous “weasel” example from Richard Dawkins’ The Blind Watchmaker (which I here adapt for my own purposes rather than his – so please spare me any complaints that I have misinterpreted him). Dawkins describes a computer program which begins with a random sequence of 28 letters and “breeds” successive copies of the sequence, in such a way that via random errors or “mutations” in the sequence together with cumulative selection, the sentence “Methinks it is like a weasel” is eventually generated. Now whether this is as useful an analogy to biological evolution as Dawkins thinks it is can be debated, but that is not to the present point. The point is rather this. Suppose we allow that a string of marks that looks like “Methinks it is like a weasel” could arise in nature via random mutation and natural selection. Indeed, suppose we even allowed for the sake of argument that such a string could result only via random mutation and natural selection. Would it follow that the English sentence “Methinks it is like a weasel” has, in that case, a completely naturalistic evolutionary explanation?

No, that wouldn’t follow at all. For an English sentence is not merely a string of marks, even if it is partly that (at least when written). It also has a semantic content, and an evolutionary process of the sort described would no more generate that content by itself than my spilling ink on the ground in a way that left a set of shapes that looked vaguely like the word “cat” would by itself generate the actual word “cat,” semantic content and all. The existence of the marks – whether the marks making up the word “cat” or those making up the sentence “Methinks it is like a weasel” -- is a necessary condition for the existence of the (written) word or sentence, but it is not a sufficient condition. So, to explain the origin of a sequence of marks is simply not by itself to explain the origin of a certain English sentence.

In the same way, to explain how sensation and mental imagery might have developed via natural selection is simply not by itself to explain the origin of human thought, even if it is part of the story and even if it were allowed that the relevant material structures and processes could not have come about in any other way. The same could be said of evolutionary explanations of whatever purported symbolic processing mechanisms cognitive scientists might claim to uncover. Such mechanisms are really all sub-conceptual and not truly “cognitive” at all; for they are all, in effect, at the level of what A-T philosophers mean when they speak of sensation and imagination, insofar as computational symbols are of themselves no more universal or determinate in their content than mental images or words are. These mechanisms may track our intellectual operations in a rough way, but they can never in principle either exhaust those operations or even exactly track them, since there is always some slack between conceptual content on the one hand and material symbols on the other. (Again, these are themes I have explored at greater length elsewhere, including in this post and many other previous posts.)

To make a human being, then, it is not enough to make something having all the sub-conceptual or sub-intellectual capacities of the human body. An animal having all those capacities may well look like a human being, and indeed have all the genetic and phenotypic attributes of a human being short of those phenotypic traits indicative of intellectual activity, such as language. Perhaps it would look and act like the apparently sub-rational “humans” in the original Planet of the Apes movie. But it would not be a human being in the sense in which A-T philosophers and Catholic theology understand “human being.” For our nature is simply not exhausted by whatever traits flow from our genetic endowment. “Human being” as used in A-T philosophy and Catholic theology is a metaphysical concept, and does not correspond exactly to (even if it overlaps with) the modern biological concept homo sapiens sapiens. (In fact, some A-T philosophers would hold that the specific genetic and phenotypic traits typical of homo sapiens sapiens are not even essential to human beings considered as a metaphysical category: Anything that was both animal and rational would arguably be “human” in the relevant sense, even if it had a body plan radically different from ours. See Oderberg’s Real Essentialism for a useful discussion.)

The origin of man

What has been said so far is along the lines of the sort of views you’ll find in Scholastic writers of the period of Pope Pius XII’s Humani Generis, and it reflects the pope’s teaching in that encyclical that:

[T]he Teaching Authority of the Church does not forbid that, in conformity with the present state of human sciences and sacred theology, research and discussions, on the part of men experienced in both fields, take place with regard to the doctrine of evolution, in as far as it inquires into the origin of the human body as coming from pre-existent and living matter - for the Catholic faith obliges us to hold that souls are immediately created by God.

However, the pope goes on to say:

When, however, there is question of another conjectural opinion, namely polygenism, the children of the Church by no means enjoy such liberty. For the faithful cannot embrace that opinion which maintains that either after Adam there existed on this earth true men who did not take their origin through natural generation from him as from the first parent of all, or that Adam represents a certain number of first parents. Now it is in no way apparent how such an opinion can be reconciled with that which the sources of revealed truth and the documents of the Teaching Authority of the Church propose with regard to original sin, which proceeds from a sin actually committed by an individual Adam and which, through generation, is passed on to all and is in everyone as his own.

This is the passage John highlights as problematic. Perhaps he thinks that what the pope is saying is that enquiry into an evolutionary explanation of human origins is permissible only to the extent that it might confirm, or at least be compatible with, the claim that evolution somehow generated exactly two human beings, one male and one female, from pre-human ancestors. And since such a claim has been falsified (so John’s argument continues), Pius’s concession can be seen to have been too modest. Given that the earliest human population could not have numbered less than 10,000 or so, a much more radical rethinking of human origins is now necessary.

But in fact no such rethinking is necessary, and Pius XII was making no such claim. Notice that what the pope opens the door to is the possibility in principle of an evolutionary explanation of the human body, specifically, not of human beings full stop. Nor does the pope say that exactly two such bodies will have to have been generated by evolution for an evolutionary explanation to be reconcilable with Catholic doctrine. He also insists that the human soul can only have come from God.

The implications of all of this should be obvious. There is nothing at all contrary to what Pius says in Humani Generis in the view that 10,000 (or for that matter 10,000,000) creatures genetically and physiologically like us arose via purely evolutionary processes. For such creatures -- even if there had been only two of them -- would not be “human” in the metaphysical sense in the first place. They would be human in the metaphysical sense (and thus in the theologically relevant sense) only if the matter that made up their bodies were informed by a human soul -- that is, by a subsistent form imparting intellectual and volitional powers as well as the lower animal powers that a Planet of the Apes-style “human” would have. And only direct divine action can make that happen, just as (for A-T) direct divine action has to make it happen whenever one of us contemporary human beings comes into existence.

Supposing, then, that the smallest human-like population of animals evolution could have initially produced numbered around 10,000, we have a scenario that is fully compatible with Catholic doctrine if we suppose that only two of these creatures had human souls infused into them by God at their conception, and that He infused further human souls only into those creatures who were descended from this initial pair. And there is no evidence against this supposition.

This scenario raises all sorts of interesting questions, such as whether any of these early humans (in the metaphysical sense of having a human soul) mated with some of the creatures who were (genetically and, in part, phenotypically) only human-like. (If any of the latter looked like Linda Harrison in Planet of the Apes, the temptation certainly would have been there.) Mike Flynn and Kenneth Kemp have some things to say about this, but it does not affect the point at issue here, which is that there is nothing in the biological evidence that conflicts with the doctrine that the human race began with a single pair -- when that doctrine is rightly understood, in terms of the metaphysical conception of “human being” described above.