Where the Conflict Really Lies: Science, Religion, and Naturalism (38 page)

David Hume, that great patron of skeptics, thought he detected a philosophical problem here:

As to past
Experience
, it can be allowed to give
direct
and
certain
information of those precise objects only, and that precise period of time, which fell under its cognizance: but why this experience should be extended to future times, and to other objects, which for aught we know, may be only in appearance similar; this is the main question on which I would insist. The bread, which I formerly ate, nourished me; that is, a body of such sensible qualities was, at that time, endued with such secret powers: but does it follow, that other bread must also nourish me at another time, and that like sensible qualities must always be attended with like secret powers?
⁴⁵

Right; it doesn’t follow. There are plenty of possible worlds that match the actual world up to the present time, but then diverge wildly, so that inductive inferences would mostly fail in those other worlds. There are as many of those counter-inductive worlds as there are worlds in which induction will continue to be reliable. It is by no means inevitable that inductive reasoning should be successful; its success is one more example of the fit between our cognitive faculties and the world.

Hume goes on to claim that there is no rational foundation for this sort of reasoning, and that inductive reasoning is not in fact rational. Is this correct? Say that a kind of reasoning is rational, for us, just if a human being with properly functioning cognitive faculties (properly functioning
ratio
or reason) would engage this kind of reasoning; if so Hume is wrong. We human beings, including those among us with properly functioning cognitive faculties, are inveterately addicted to inductive reasoning. And this is another example of fit between our cognitive faculties and the world in which we find ourselves. Like the others, this fit is to be expected given theism. God has created us in his image; this involves our being able to have significant knowledge
about our world. That requires the
adequatio intellectus ad rem
(the fit of intellect with reality) of which the medievals spoke, and the success of inductive reasoning is one more example of this
adequatio
. According to theism, God has created us in such a way that we reason in inductive fashion; he has created our world in such a way that inductive reasoning is successful. This is one more manifestation of the deep concord between theism and science.

Scientific theories, so we are told, are underdetermined by the evidence. This just means that these theories
go beyond
the evidence; they are not merely compendious ways of stating the evidence. Very few experiments of the sort Galileo conducted with those balls of different weights have been conducted; we still think his results hold for all or nearly all objects. The evidence for Newton’s laws (as applied to middle-sized objects moving at moderate velocities with respect to each other) is extensive, but the laws go far beyond the evidence, applying to future cases of motion as well as past but unobserved cases. The same goes for any scientific theory. For example, the actual experimental evidence for general relativity is fairly slim, and is compatible with many theories inconsistent with general relativity. The evidence for Newton’s law of gravitation is compatible with a “law” such as

Any two physical objects attract each other with a force conforming to G m
₁
m
₂
over r
²
except on Thursdays, when G is replaced by G*, (where G* a value indistinguishable from G by current methods).

One way to think of this is in terms of the curve fitting problem. As Leibniz already pointed out in the seventeenth century, for any finite set of observations of the path of a comet, infinitely many different curves can be found to fit; he also points out that given any finite set of statistics, there will be infinitely many statistical hypotheses fitting the facts.
⁴⁶

So why do we choose certain hypotheses to endorse, when there are infinitely many compatible with our evidence? Because these hypothesis, as opposed to others, display the so-called
theoretical virtues
. Among these virtues the following have been proposed: simplicity, parsimony (which may be a form of simplicity), elegance or beauty, consilience (fit with other favored or established hypotheses), and fruitfulness. Nobel laureate Steven Weinberg suggests that the beauty of general relativity is what led him and others to embrace it, well before there was serious evidence for it:

I remember that, when I learned general relativity in the 1950s, before modern radar and radio astronomy began to give impressive new evidence for the theory, I took it for granted that general relativity was more or less correct. Perhaps all of us were just gullible and lucky, but I do not think that is the real explanation. I believe that the general acceptance of general relativity was due in large part to the attractions of the theory itself—in short, to its beauty.
⁴⁷

Simplicity (which is involved in beauty) is often thought of as particularly important.
⁴⁸
Thus Einstein:

With every new important advance the researcher here sees his expectations surpassed, in that those basic laws are more and more simplified under the pressure of experience. With astonishment he sees apparent chaos resolved into a sublime order that is to be attributed not to the rule of the individual mind, but to the constitution of the world of experience; this is what Leibniz so happily characterized as “pre-established harmony.”
⁴⁹

Complicated, gerrymandered theories are rejected. Complex Rube Goldberg contraptions are ridiculed. When confronted with a set of data plotted on a graph, we draw the simplest curve that will accommodate all the data. There are any number of other curves that will accommodate the data; but these will be rejected in favor of the simplest alternative. Physics gives us a law of conservation of energy: energy is conserved in all closed physical systems. This is compatible with our evidence; but of course so are indefinitely many other “laws”—for example, energy is conserved in all closed physical systems except in months whose names start with “J,” in each of which there are exactly twelve undetectable exceptions.

Simplicity, therefore, is a crucially important part of our intellectual or cognitive architecture—or rather,
preference
for simplicity is. That the world be relevantly simple is also required, of course, for the success of science. It isn’t a necessary truth, however, that simple theories are more likely to be true than complex theories. Naturalism gives us no reason at all to expect the world to conform to our preference for simplicity. From that perspective, surely, the world could just as well have been such that unlovely, miserably complex theories are more likely to be true.

Theism with its doctrine of the
imago dei
, on the other hand, is relevant in two quite distinct respects. First, insofar as we have been created
in God’s image, it is reasonable to think our intellectual preferences resemble his. We value simplicity, elegance, beauty; it is therefore reasonable to think that the same goes for God. But if he too values these qualities, it is reasonable to think this divine preference will be reflected in the world he has created. Second, what we have here is another example of God’s having created us and our world in such a way that there is that
adequatio intellectus ad rem
. We are so constituted that our intellectual success requires that the world be relevantly simple; the world is in fact relevantly simple. This fit is only to be expected on theism, but is a piece of enormous cosmic serendipity on naturalism. It is therefore one more way in which there is deep concord between theistic religion and science. Surely the world could have been such that unlovely, miserably complex theories are more likely to be true. It could have been such that there is insufficient simplicity for science, at least our human brand of science, to be successful.

A final but crucial point. Science, obviously, has a substantial empirical element; in this way it contrasts with, for example, philosophy and literary criticism. (Indeed, many take this as a reason for invidious comparisons between philosophy and science.) In science we don’t sit in our armchair and just try to figure out the laws of motion; nor do we consult the ancients. Instead we take a look. There is a famous (but surely apocryphal) story about some medieval followers of Aristotle who wanted to know how many teeth a horse has. It didn’t occur to them to open a horse’s mouth and count its teeth; they tried to deduce the answer from first principles (and Aristotle’s works). This is the opposite of the scientific impulse. Rather, we take a look, or in more abstruse cases, think up theories that can be tested in experience. It isn’t true, of course, that every
scientific assertion, just by itself, is testable or empirically verifiable or falsifiable. The proposition
there are electrons
is a scientific assertion; by itself, however, it has no empirical consequences and isn’t testable. What yields empirical predictions, and thus is subject to empirical test, are whole theories; such a theory will include the assertion that there are electrons, and will also imply consequences that can be confronted with experience.

This means that we can’t take assertions one by one and declare them scientific or unscientific, depending on whether they are empirically testable. The devotees of intelligent design claim, naturally enough, that an intelligent designer is involved in the creation of our world; others insist that this proposition is untestable and hence not properly part of science. Well, perhaps that proposition, like the proposition that there are electrons, isn’t empirically verifiable or falsifiable
just by itself
; but many propositions entailing or including that one are testable. For example, the proposition
an intelligent designer has designed and created 800-pound rabbits that live in Cleveland
is falsifiable, and indeed false. On the other hand, the proposition
an intelligent designer has designed and created horses
entails that there are horses, and thus, like electron theory, has empirical consequences that are in fact true. It is difficult
in excelsis
to say precisely what testability is, or how we should think about it; nevertheless there is no doubt that this link to the empirical is an essential part of modern science.

Here there is another crucial connection between theistic belief and modern science. According to theism, God has created the world; but divine creation is
contingent
. Many of God’s properties—his omniscience and omnipotence, his goodness and love—are, as theists think of it,
essential
to him: he has them in every possible world in which he exists. (And since, according to most theistic thought, God is a necessary being, one that exists in every possible world, he has those properties in every possible world.) Not so, however, with God’s properties of being a creator and having created our world.
God is not obliged, by his nature or anything else, to create the world; there are plenty of possible worlds in which he doesn’t create a world outside himself. Instead, creation is a free action on his part. Furthermore, given that he
does
create, he isn’t obliged to do so in any particular way. He wasn’t obliged to create people or electrons; he wasn’t obliged to create matter in such a way that Newton’s laws of motion hold for middle-sized objects moving at moderate velocities with respect to each other; he wasn’t obliged to create a world in which quantum mechanics or relativity theory would be true. That he has created a world outside of himself at all, and that the world he has created displays the particular character and laws it does display—these are contingent matters.

It is this doctrine of the contingency of divine creation that both underlies and underwrites the empirical character of modern Western science.
⁵⁰
The realm of the necessary is the realm of a priori knowledge, knowledge that is prior to experience. Here we have mathematics and logic and much philosophy. We know that 3+1 = 4, but not by way of empirical investigation; we don’t assemble a lot of pairs of groups of three things with groups of one thing, and then count up the members of those pairs to see if they make four. We can simply see that 3+1 = 4. In the same way, we know that if all terriers are dogs and all dogs are animals, then all terriers are animals. Again, we know this a priori; we don’t have to assemble packs of terriers, note that they are all dogs, and then check to see whether they are animals. Our knowledge of what is logically necessary is a priori.
⁵¹
What is contingent,
on the other hand, is the domain or realm of a posteriori knowledge, knowledge that requires experience, the sort of knowledge produced by perception, memory, the sort of knowledge produced by the empirical methods of science.
⁵²
We can’t just sit down and figure out whether Newton’s laws of motion apply; we have to resort to observation and experience. We can’t tell a priori how many teeth horses have or whether heavy objects fall faster than light objects; we must take a look.
⁵³

This relationship between the contingency of creation and the importance of the empirical, in science, was recognized very early; indeed, the former is the source of the latter. Thus Roger Cotes, from the preface he wrote for the second edition of Newton’s
Principia Mathematica
:

Without all doubt this world, so diversified with that variety of forms and motions we find in it, could arise from nothing but the perfectly free will of God directing and presiding over all.