The Realism vs. Anti-Realism Debate
The mid-1980's saw a transformation of the debate over
"scientific rationality" which had been unleashed by Thomas
Kuhn's (1922 – 1996), His work was perceived
to challenge to the traditional claims of philosophers of science, that science
was a preeminently “rational” form of inquiry (indeed perhaps the most rational
if not the only rational form), where theory acceptance is
determined solely by evidence and reasoning. Here Kuhn is putting himself in direct
opposition to Philosopher of Science Karl Popper (1902 – 1994).
While Kuhn himself sought to differentiate his view from
that attributed to him by his most radical defenders, his introduction of the
"sociological thesis" to account for how (actual) science proceeds
challenged the traditional understanding.
It effectively accounts for scientific evolution in largely non-evidential
non-rational terms (e.g. social, economic, political, historical,
personal egos, etc.). It instead
provided a sociological account of the behavior of concrete individuals in
specific social situations. The result of
this pro-sociology of science camp was to deconstruct philosophy of science (at
least as traditionally conceived). The
Popperian account of rational scientific progress was at best a mythological
rational reconstruction of actual scientific evolution.
Many philosophers of science sought to distance
themselves, in varying degrees, from the extreme relativism implied by the most
radical reading of Kuhn and this version of Scientific Antirealism. However, among the sociologists of science by
contrast, there was general enthusiastic agreement on the relativity of
scientific beliefs, even though there was considerably less agreement as to
what they were relative to.
The philosophers rejecting the anti-rational relativistic
account of science found themselves disagreeing less and less over whether or
not science exhibited a "rationality." In that sense they were almost all
"pro-rationality" in alliance against their relativist/sociological
foes, but they found themselves in serious disagreement over the nature
of that "rationality." On one
side, there emerged a group who defended scientific rationality in the name of
what has been called "scientific realism" or, in this context, simply
"realism." On the other side,
there emerged those who, while still defending the rationality of science,
embraced an anti-realist stance toward the deliverances
of science.
What is Realism?
Realist justifications of scientific rationality are
anchored in the claim that scientific knowledge aspires to discover “the truth”
about how things really are, where “truth” is cashed out largely in
correspondence terms. Moreover, these Realists
claim that, if it is rational to accept a theory, it is equally rational to
believe in the existence of the "theoretical entities" posited by
such a theory, even if such theoretical entities themselves cannot be directly
observed.
"Realism" can be thought of as a philosophical
theory answering the old question which we called the "Problem of
Authority": how can we justify the claim that it is rational to believe
scientific explanations? The Realist
answers by saying the ultimate authority which justifies the rationality of
scientific beliefs is simply that they are true in the sense of
"truth" as a relation of correspondence between what we believe to be
the case and what in reality is the case.
Alternatively realism can be thought of as a theory about
the aim of science: scientific theories aspire to tell us the truth about the
world. Thus it is an Axiological theory
about science which holds that all science has one fixed goal: finding out the
truth about the nature of reality. It ought
to be looking for and discovering the truth.
And “good” theories are the ones that accomplish this goal or come near.
Scientific methodology, the Realist claims, is adopted to
the extent that it proves an effective method of attaining the truth, and all
other goals to which scientific knowledge may aspire are ultimately dependent
upon how things really are. The Realist
may well admit that there may be more than one way to describe the world, but
the ones which are selected are selected because they are, of their competing
rivals at any point in history, the closest to the truth about the nature of
reality.
Furthermore, the history of science is also rational in
the sense that it represents progress in getting closer to the
truth about how things really are; today's beliefs are closer to that goal than
were the discarded beliefs of former times.
Who are the Realists' opponents?
Sociologists who accept some form of the sociological
thesis of Kuhn reject realism and its story about progress as "approaching
the truth" as a philosophical myth (and no doubt account for the myth
making tendency of philosophers by some social/psychological explanation). It is typical of some philosophers who hold
this sociological outlook to speak of "Philosophy" as having been
terminated with the end of the "modern" period, so these
"postmodern" thinkers disown the label "Philosopher."
Their viewpoint might be labeled a
"non-philosophical anti-realism" or, more descriptively, a
"social constructivist anti-realism." This outlook is most commonly found in
programs or departments which are typically called "Science Studies"
programs, by which is intended a cluster of different social sciences applied
to the study of scientists and their activities, including not only
"sociology," but also psychology, economics, linguistics, cognitive
science, gender and ethnic studies, etc. This group is one of the opponents of Realism.
On the philosophers' side, however, there also flourished
in the 1980's a wide variety of anti- or non- realisms which opposed realism in
a way quite differently from the social constructivists. These philosophical anti-realists saw the
realist defense of rationality as anchored in truth as tantamount to handing
the sociologists victory. It is, they
maintained, because scientific rationality has been misconstrued by Realists in
terms of "mirroring nature" (i.e. the correspondence theory of
"truth") that the relativists are able to gain easy victories. For these "philosophical anti-realists,"
scientific rationality needs to be de-coupled from talk of "truth"
and "reality" and re-expressed in terms of "empirical
adequacy" and a variety of "pragmatic" criteria.
These anti-realist philosophers agree with the
(non-philosophical) sociologist anti-realists that scientific beliefs are
largely a "construction," but, in opposition to the sociologists, they
deny that this construction is explained by social factors "external"
to scientific knowledge. Instead, they
seek to justify a scientific rationality according to which a belief is adopted
because it makes correct predictions (empirically validated) about observable
outcomes and displays other pragmatic virtues such as simplicity, breadth of
scope, fertility, etc.
The philosophical anti-realists are today's descendants
of older empiricists, and they perceive themselves as such. Their empiricism makes them wary of
"metaphysical" claims about the "nature of reality" and
enthusiastic for "observational claims" which can be terminated in an
actual experiential state in which some piece of data is recorded. Only this latter class of observational
statements need be accorded "truth" and their truth is settled
directly by an appeal to experience. (Note the resonance here with the earlier
reductive empiricists Locke, Hume, etc.)
They are said to be "directly verified" by experience. All other statements which scientists make
about what is not directly observed need not be thought of as
"true" (or "false") but only as "successful" as a
means for predicting or deducing "observation statements."
Any terms in theories which appear to refer to
"unobservable" entities, states, or processes, should not be
understood as referring to real events behind the screen of phenomena which we
observe. Such "putatively referring
terms" (appear to refer but don't) are constructs of our theories, the
acceptance of which is solely a function of their empirical adequacy (getting
the numbers right), with the usual pragmatic virtues providing further back up
when there's a choice to be made between empirically equivalent theories. Thus these anti-realists may also be called
"empiricist/pragmatist anti-realists."
This empiricist/pragmatist anti-realism is
pro-rationality (unlike sociological anti-realism), but anti-truth; throughout
the eighties and well into the nineties, philosophy of science centered on
debates between these anti-realists and realist defenders of scientific
rationality.
What reasons do Realists give for their view?
Realists see philosophical anti-realists as making the
classical pragmatists' blunder of confusing the process by which human inquiry
leads to a particular belief as the rational belief to accept with what makes
that belief acceptable. The
pragmatist/empiricist position of the anti-realists provides a candidate for
addressing the first issue (how we decide what to accept), but ignores the
second (what makes that belief acceptable).
We may decide to accept a belief based on empirical adequacy the
Realists maintain, but what makes the belief acceptable is that
such beliefs are more likely to be true.
From the empiricist/pragmatist anti-realists' point of
view, there is no difference between these two; what makes a belief acceptable
is just that: the process by which human inquiry leads to a particular belief
as the rational one to accept. The Realist
disagrees: what leads a scientist to accept a belief is the empirical evidence
(combined with the pragmatic virtues), with that much of what the anti-realists
say the realists agree, but the Realist wants to add: what makes the process of
inquiry settle on that particular belief is our commitment to scientific progress. We are convinced that, out of
currently competing beliefs, this one is closest to “the truth.”
Scientific Realism and Inference To The Best Explanation
(IBE)
Further, the Realists asks, “Why would a particular
theory be more successful than its rivals at "getting the
numbers right"? In other words, “What
causes this particular theory to be so ‘empirically adequate;"? The best way to explain the marvelous
empirical adequacy of our best theories, the Realist contends, is to claim that
(of competing rivals), they are closest to the truth. So, by "inference to the best
explanation" realism is demanded to explain the "success" of
science.
The anti-realists say we accept a theory because of its
success, and realists do not dispute that. But the anti-realists do not address what
makes it so successful. Therefore, on
their anti-realist account, so the Realists tell us, that success is
"miraculous." But, the Realist
continues, there are no miracles, so the anti-realist account is unacceptable.
(This is known as the "no miracles" argument.)
Realists see scientific inquiry as discovery while
anti-realists see it as invention. For
the Realist there is a "way things really are" and science is trying
to find out what it is; it endeavors to discover the "truth." For
the anti-realist, there is no one way things are apart from how our theories
construct them. All "worlds" are constructions of
how we view the world, of our theories. Therefore,
there is no "way things are" to discover the truth about. To think of theories as "true" or
"false" descriptions of an unseen world "beneath" or
"behind" the phenomena we observe is to mistake what theories
are. Scientific theories are not
attempts to describe what is (allegedly) the real cause of phenomena by
"representing" or "mirroring" an independent
"reality" as it exists apart from the phenomena we experience. They are invented by theoreticians to serve
as tools for making observational predictions about empirical phenomena.
Retorts of the Anti-realists
The anti-realist is unimpressed by this realist
"explanation" of the success of science simply because, given an
anti-realist understanding of scientific theories, scientific theories really
do not "explain" anything at all; they are just successful
predictors, i.e. "tools" or "instruments" for, as
scientists often say, "getting the numbers (in other words the
observational data) right." The Realist
craves "explanation"; thus the Realist regards the extraordinary
accuracy of contemporary scientific theories as a phenomenon that needs an
explanation; and, so the realist argues, the best explanation we can provide
for this marvelous "success" is that such theories are (at least
close to) the truth about reality. The anti-realist regards that Realist
craving for "explanation" as something we need to learn to do
without.
Varieties of Realists
Defenders of scientific realism are by no means all
agreed upon a single doctrine. There are
many ways of distinguishing different realist views. One such distinction is between "entity
realists" and "theory realists":
Entity Realists
"Entity realists" defend the
"reality" of the entities to which at least some purely theoretical
terms refer and de-emphasize the problems of "truth" as
correspondence to reality. They will
agree with anti-realists that theories may be only "useful
instruments" more than "approximately true descriptions" of an
unobservable reality, but these theories enable us to discover real hidden
(unobservable) processes and entities causing observable phenomena. Entity realists tend to be naturalists and may
emphasize experiment over theory as the road to discovery.
Theory Realists
"Theory realists" on the other hand pursue
theories of "correspondence" and reference and theories of
approximate truth, and will stress logical and linguistic arguments for truth.
Contemporary realists may be choosy about what theories or entities to regard "realistically"; in a naturalistic vein one may argue that a realistic interpretation is itself a function of empirical evidence and thus as evidence changes what we may rationally regard as real also changes.
Entity realists hold that what one is rationally compelled to believe the existence of some of the unobservable entities postulated by our best scientific theories, but one is not obligated to believe that everything that our best theories say about those entities is true.
Nancy Cartwright, for example, argues that we are compelled to believe in those entities that figure essentially in causal explanations of the observable phenomena, but not in the theoretical explanations that accompany them. The primary reason she gives is that causal explanations, e.g., that a change in pressure is caused by molecules impinging on the surface of a container with greater force after heat energy introduced into the container increases the mean kinetic energy of the molecules, make no sense unless you really think that molecules exist and behave roughly as described.
Cartwright claims that you have offered no explanation at all if you give the preceding story and then add, "For all we know molecules might not really exist, and the world simply behaves as if they exist."
Theoretical explanations, on the other hand, which merely derive the laws governing the behavior of those entities from more fundamental laws, are not necessary to believe, since a multiplicity of theoretical laws can account for the phenomenological laws that we derive from experiment. Cartwright argues that scientists often use different and incompatible theoretical models based on how useful those models are in particular experimental situations. If this is so, scientists cannot be committed to the truth of all their theoretical models. However, scientists do NOT admit incompatible causal explanations of the same phenomenon. According to Cartwright, that is because a causal explanation cannot explain at all unless the entities that play the causal roles in the explanation exist.
Cartwright's argument depends on a certain thesis about explanation. Explanations can either cite causes or can be derivations from fundamental laws. She adds to this an associated inference rule : one cannot endorse a causal explanation of a phenomenon without also assenting to the existence of the entities that, according to the explanation, play a role in causing the phenomenon. As Cartwright sometimes puts it, she rejects the rule of Inference to the Best Explanation, but accepts a rule of Inference to the Most Probable Cause.
Van Fraassen rejects the notion that a causal explanation
cannot be acceptable unless one also accepts that the entities that the causal
explanation postulates actually exist. On
the contrary, if what is requested in the circumstances is information about
causal processes according to a particular scientific theory, it will be no
less explanatory if we merely accept the theory (i.e. believe it to be empirically
adequate) rather than believe that theory to be “true,” or believe in
the ontological reality of the unobservable entities postulated by that theory.
Thus, the constructive empiricist can
reject Cartwright's argument since he holds a different view of what scientific
explanation consists in.
Hacking takes a different route in arguing to an entity realist position. Hacking argues that the mistake that Cartwright and van Fraassen both make is concentrating on scientific theory rather than experimental practice. His approach can be summed up in the slogans "Don't Just Peer, Interfere" (with regard to microscopes), and "If you can manipulate them, they must be real" (with regard to experimental devices that use microscopic particles such as electrons as tools).
Two Cases
In his article, "Do We See Through a Microscope?" (Churchland and Hooker, eds., 1985, Images of Science), Hacking argues that what convinces experimentalists that they are seeing microscopic particles has nothing to do with the theory of those particles or of how a microscope behaves, but that they can manipulate those particles in very direct and tangible ways to achieve certain results.
·
The ability to see through a microscope is
acquired through manipulation (what is an artifact of the instrument and what
is reality are learned through practice).
·
We believe what we see because by manipulation
we have found the preparation process that produces these sights to give stable
and reliable results, and to be related to what we see macroscopically in
certain regular ways (the Grid Argument, the electron beam arguments of
"Experimentation and Scientific Realism," in Kourany)
·
We believe what we see through a particular
instrument is reliable because we can invent new and better ways of seeing it
(optical microscopes, ultraviolet microscopes, electron microscopes, etc.)
Hacking's argument contains three elements, that
a) Manipulation causes cognitive changes that give us new perceptual abilities.
b) We can manipulate the world in such a way as to create microstructures that have the same properties as macrostructures we can observe.
c) (From
a and b) The convergence of the various instruments on the same visual results
gives us additional reason to believe that what we are seeing is real, not an
artifact of any particular instrument.
The final element (c) seems similar to the convergence argument we looked at last time, when we were discussing IBE. There is a difference, however, since what is at issue is not whether a single scientific theory implies things that are verified under many independent circumstances, but whether we are convinced that we are seeing something based on the fact of stable features using different viewing techniques. Nevertheless, it is a no-miracles argument from coincidence. Wouldn't it be a miracle if all these independent viewing techniques shared stable structural features and those features weren't really present in the microscopic specimen? This stands or falls on the same grounds as were discussed last time.
However, that is not all that Hacking has at his
disposal. His greatest strength is discussing how we acquire new modes of
perception by using instruments to manipulate a world we cannot see (“a” from
above). In his words, we don't see through a microscope, we see with a
microscope. That is something that must be learned by interacting with the
microscopic world, just as ordinary vision is acquired by interacting with the
macroscopic world around us.
In addition, Hacking wants to argue that we come to manipulate things in ways that do not involve direct perception. This is where the example of using electrons to check for parity violation of weak, neutral currents comes in. In this case, Hacking argues that it might have once been the case that the explanatory virtues of atomic theory led one to believe in their existence; but now we have more direct evidence. We can now use electrons to achieve other results, and thus we are convinced of the existence of entities with well-defined, stable causal properties.
That does not mean that we know everything there is to know about those particles (thus, we may disbelieve any of the particular theories of the electron that are in existence); however, that there are entities with certain causal properties is shown by experience, by manipulating electrons to achieve definite, predictable results. (Hence the slogan, "If you can manipulate them, they must be real.") This is why Hacking, like Cartwright, is an entity realist, but not a realist about scientific theories.
Scientific Realism Vs. Constructive Empiricism
Let us examine now a closely related topic: the debate between Scientific Realism and Constructive Empiricism. This debate was provoked primarily by the work of Bas van Fraassen, whose critique of scientific realism and defense of a viable alternative, which he called constructive empiricism, first reached a wide audience among philosophers with the publication of his 1980 book The Scientific Image[1].
What Is Scientific Realism
Keep in mind that Scientific Realism insists that we must distinguish between the "aims of science" and the motives that individual scientists have for developing scientific theories. Individual scientists are motivated by many diverse things when they develop theories, such as fame or respect, getting a government grant, and so on. The aims of the scientific enterprise are determined by what counts as success among members of the scientific community, taken as a whole.
Van Fraassen's analogy: The motives an individual may have for playing chess can differ from what counts as success in the game (i.e., putting your opponent's king in checkmate). For the scientific realist, to count as fully successful a scientific theory must provide us with a literally true description of what the world is like. That is the aim of science.
Realists are not so naive as to think that scientists' attitudes towards even the best of the current crop of scientific theories should be characterized as simple belief in their truth. After all, even the most cursory examination of the history of science would reveal that scientific theories come and go; moreover, scientists often have positive reason to think that current theories will be superseded, since they themselves are actively working towards that end. (Example: The current pursuit of a unified field theory, or "theory of everything.")
Since acceptance of our current theories is tentative, realists, who identify acceptance of a theory with belief in its truth, would readily admit that scientists at most tentatively believe that our best theories are true. To say that a scientist's belief in a theory is "tentative" is of course ambiguous: it could mean either that the scientist is somewhat confident, but not fully confident, that the theory is true; or it could mean that the scientist is fully confident that the theory is approximately true. To make things definite, we will understand "tentative" belief in the former way, as less-than-full confidence in the truth of the theory.
Constructive Empiricism: An Alternative To Scientific
Realism
There are two basic alternatives to scientific realism, i.e., two different types of scientific anti-realism. That is because scientific realism as just described asserts two things, that scientific theories
(1) should be understood as literal descriptions of the what the world is like, and
2) so construed, a successful scientific theory is one that is true.
Thus, a scientific anti-realist could deny either (1) that theories ought to be construed literally, or that (2) theories construed literally have to be true to be successful.
A "literal" understanding of a scientific theory is to be contrasted with understanding it as a metaphor, or as having a different meaning from what its surface appearance would indicate. For example, some people have held that statements about unobservable entities can be understood as nothing more than veiled references to what we would observe under various conditions (e.g., the meaning of a theoretical term such as "electron" is exhausted by its "operational definition.")
Van Fraassen is an anti-realist of the second sort: he agrees with the realist that scientific theories ought to be construed literally (#1), but disagrees with them (on #2) when he asserts that a scientific theory does not have to be true to be successful. Van Fraassen espouses a version of anti-realism that he calls "Constructive Empiricism." This view holds that
(1) science aims to give us theories that are empirically adequate, and
(2) acceptance of a scientific theory involves the belief that it is empirically adequate.
(And one may/should remain uncommitted to the theory’s truth. This further contention plays no role in the exercise of science.)
As was the case above, one can tentatively accept a scientific theory by tentatively believing that the theory is empirically adequate.
A scientific theory is "empirically adequate" if it gets things right about the observable phenomena in nature. Phenomena are "observable" if they could be observed by appropriately placed beings with sensory abilities similar to those characteristic of human beings. On this construal, many things that human beings never have observed or ever will observe count as "observable." On this understanding of "observable," to accept a scientific theory is to believe that it gets things right not only about the empirical observations that scientists have already made, but also about any observations that human scientists could possibly make (past, present, and future) and any observations that could be made by appropriately placed beings with sensory abilities similar to those characteristic of human scientists.
The Notion Of Observability
Constructive empiricism requires a notion of "observability." Thus, it is important that we be as clear as possible about what this notion involves for van Fraassen. Van Fraassen holds two things about the notion of observability:
(1) Entities that exist in the world are the kinds of things that are observable or unobservable.
There is no reason to think that language can be divided into theoretical and observational vocabularies, however. We may describe observable entities using highly theoretical language (e.g., VHF receiver," "mass," "element," and so on); this does not, however, mean that whether the things themselves (as opposed to how we describe or conceptualize them) are unobservable or not depends on what theories we accept. Thus, we must carefully distinguish between observing an entity from observing that an entity exists meeting such-and-such a description. The latter can be dependent upon theory, since descriptions of observable phenomena are often "theory-laden." However, it would be a confusion to conclude from this that the entity observed is a theoretical construct.
(2) The boundary between observable and unobservable entities is vague.
There is a continuum from viewing something with glasses, to viewing it with a magnifying lens, with a low-power optical microscope, with a high-power optical microscope, to viewing it with an electron microscope. At what point should the smallest things visible using a particular instrument count as "observable?" Van Fraassen's answer is that "observable" is a vague predicate like "bald" or "tall." There are clear cases when a person is bald or not bald, tall or not tall, but there are also many cases in between where it is not clear on which side of the line the person falls. Similarly, though we are not able to draw a precise line that separates the observable from the unobservable, this doesn't mean that the notion has no content, since there are entities that clearly fall on one side or the other of the distinction (consider sub-atomic particles vs. chairs, elephants, planets, and galaxies). The content of the predicate "observable" is to be fixed relative to certain sensory abilities. What counts as "observable" for us is what could be observed by a suitably placed being with sensory abilities similar to those characteristic of human beings (or rather, the epistemic community to which we consider ourselves belonging). Thus, beings with electron microscopes in place of eyes do not count.
Arguments In Favor Of Scientific Realism: Inference To
The Best Explanation (IBE)
Now that we have set out the two rival positions, let us examine the arguments that could be given in favor of scientific realism. An important argument that can be given for scientific realism is that we ought rationally to infer that the best explanation of what we observe is true. This is called "inference to the best explanation." (IBE) The argument for this view is that in everyday life we reason according to the principle of inference to the best explanation, and so we should also reason this way in science. The best explanation, for example, for the fact that measuring Avogadro's number (a constant specifying the number of molecules in a mole of any given substance) using such diverse phenomena as Brownian motion, alpha decay, x-ray diffraction, electrolysis, and blackbody radiation gives the same result is that matter really is composed of the unobservable entities we call molecules. If it were not, wouldn't it be an utterly surprising coincidence that things behaved in very different circumstances exactly as if they were composed of molecules?
This is the same kind of reasoning that justifies belief that an apartment has mice. If all the phenomena that have been observed are just as would be expected if a mouse were inhabiting the apartment, isn't it then reasonable to believe that there's a mouse, even though you've never actually seen it? If so, why should it be any different when you are reasoning about unobservable entities such as molecules?
Van Fraassen's response To IBE
Van Fraassen's response is that the scientific realist is assuming that we follow a rule that says we should infer the truth of the best explanation of what we have observed. This is what makes it look inconsistent for a person to insist that we ought not to infer that molecules exist while at the same time insisting that we ought to infer that there is a mouse in the apartment. But van Fraassen counters, “Why not characterize the rule we are following differently?”--i.e., that we infer that the best explanation of what we observe is empirically adequate.
If that were the case, we should believe in the existence of the mouse, but we should not believe anything more of the theory that matter is composed of molecules than that it adequately accounts for all observable phenomena. In other words, van Fraassen is arguing that, unless you already assume that scientists follow the rule of inference to the (truth of the) best explanation, you cannot provide any evidence that they follow that rule as opposed to following the rule of inference to the empirical adequacy of the best explanation.
The argument for scientific realism based on an appeal
to a (putative) rule of reasoning, called Inference to the Best Explanation
(IBE)
So, the scientific realist argues that convergent but independent determinations of Avogadro's number were better explained by the objective truth of the unobservable molecular hypothesis than its empirical adequacy (Salmon 1984, Scientific Explanation and the Causal Structure of the World, pages 213-227). The primary problems with that argument were
(1) the realist has given no reason to think that we, as a rule, infer the “truth” of the best explanation, rather than the “empirical adequacy: of the best explanation.
(2) it is impossible to argue for IBE as a justified rule of inference unless one assumes that human beings are, by nature, more likely to think up true explanations rather than ones that are merely empirically adequate.
There are, of course, responses a realist can make to these objections:
1) Evolution selected humans based on our ability to generate true rather than false hypotheses about the world.
2) One can accept the objection, but argue that we are somehow forced to believe the best available explanation as true.
Neither of these responses seems very convincing according to (van Fraassen 1989, Laws and Symmetry, pages 142-150).