Perspectiva Filosófica, vol. 45, n. 1, 2018
HOW TO SAVE VAN FRAASSEN’S OWN ANTIREALISM:
A MODEST PROPOSAL
_____________________________________________________________
Alessio Gava1
ABSTRACT
Bas van Fraassen’s antirealist view of science and its aim, constructive empiricism,
notoriously rests upon a distinction between observable and unobservable
entities. In order to back his empiricist stance, the Dutch philosopher put
forward his own characterization of observability. Nonetheless, he
acknowledges that the point of constructive empiricism is not lost if the line is
drawn in a somewhat different way from how he draws it. This means that
other characterizations of observability can support this antirealist stance,
provided they allow for a viable distinction between the observable and the
unobservable. The aim of this work, however, is not to propose another
characterization of observability that fits constructive empiricism, but to put
forward a little amendment to van Fraassen’s own antirealism, to the effect that
it can actually be seen as a coherent position, albeit controversial, since its
present consistency might be called into question.
Palavras-chave: antirealism, constructive empiricism, observability, realism, van
Fraassen.
RESUMO
A vertente antirrealista acerca da ciência e de seus objetivos de Bas van
Fraassen, o empirismo construtivo, repousa, como bem se sabe, sobre uma
distinção entre entidades observáveis e inobserváveis. Para suportar a sua
posição empirista, o filósofo holandês propôs uma certa caracterização da
observabilidade. Entretanto, reconhece que o ponto do empirismo construtivo
não está perdido se a linha divisória for traçada de modo diferente de como ele
mesmo a traça. Isso significa que outras caracterizações da observabilidade
podem sustentar essa stance antirealista, desde que contemplem uma distinção
viável entre o observável e o inobservável. O objetivo desde trabalho, todavia,
não é propor uma outra caracterização da observabilidade que seja adequada ao
empirismo construtivo e sim sugerir uma pequena emenda ao antirealismo de
van Fraassen, de modo que esse possa de fato ser considerado uma posição
coerente, ainda que controversa, pois sua consistência atual poderia ser
questionada.
Keywords: antirrealismo, empirismo construtivo, observabilidade, realismo, van
Fraassen.
1
Mestre e Doutor em Lógica e Filosofia da Ciência pela UFMG, formado em Física pela
"Università degli Studi di Trieste" (Itália), professor de matemática junto à Universidade
Estadual do Paraná - Campus de Apucarana.
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Introduction
If one asks what the realism vs antirealism debate in the philosophy of
science is about, a good answer comes from Anjan Chakravartty: “The essence
of the controversy between realists and antirealists concerns the possibility of
having knowledge of the unobservable” (CHAKRAVARTTY, 2007, p. xiii). In
this area of philosophy, being an antirealist means being a ‘non realist’; the
prefix ‘anti’ indicating the refusal to endorse (typically realist) epistemological
and/or ontological commitments to the unobservable entities posited by the
theories we accept and use. As a matter of fact, the standard antirealist attitude
- at least nowadays - is not the denial that unobservable entities exist, but rather
an agnostic stance towards them, to the effect that accepting a scientific theory
does not compel one to believe that it gives a true description of a putative
unobservable reality.2
It is clear that in this field ‘antirealism’ and ‘empiricism’ amount to the
same position.3 In this context, “the empiricist’s preoccupation with sense
experience takes the form of a thesis about the role of observation in science”
(SOBER 2008, p. 129), namely, that commitments to the unobservable are
supererogatory. It can be legitimately maintained, in general, that the issue of
observation and observability, although under different forms, constitutes a
central topic of both the 20th and the 21st century philosophy of science - the
realist side frequently seeming more an anti-antirealist stance than an
independent one.
If these days the interest of many authors seems to be shifting towards
structuralism, then, it should not be forgotten that any topic related to the role
of observation in science - such as trying to establish what ‘to observe’ means
or which is the scope of ‘observable’, wondering whether instrumental
detections can be considered observations or not, etc. - is still absolutely crucial
in the philosophy of science; at least for the realism/antirealism dispute.
Moreover, as Jennifer Nagel put it in the past decade, “the version of
empiricism that constitutes the most influential contribution to traditional
2
In his seminal work Empiricism, Semantics and Ontology (1950). Rudolf Carnap explicitly claimed
that the thesis of the reality of the external world is a pseudo-question. However, this same
thesis apparently underlies the debate between realism and antirealism (and philosophy of
science in general), nowadays.
3
For a comprehensive discussion of the various meanings of ‘empiricism’, with a focus on the
philosophy of science, see SOBER (2008).
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epistemology since the collapse of positivism has been put forward by Bas van
Fraassen, in support of the view of science he calls ‘constructive empiricism’”
(NAGEL 2006, p. 240).4 Constructive empiricism has been much discussed
since it came into being in 1980, with the publication of van Fraassen’s seminal
book The Scientific Image. An extensive literature on observation and
observability is part of this discussion, for these concepts play a decisive role
in the antirealist stance promoted by the Dutch philosopher; but also because
of van Fraassen’s controversial position on this matter, particularly when it gets
to the use of instruments in science.
Admittedly, while constructive empiricism is (still) recognized as a
prominent antirealist position, there is also a general dissatisfaction with van
Fraassen’s treatment of the issue of observability. His position on the matter,
however, is ancillary to the view on science and its aim that he proposed
almost forty years ago, but not part of it (see, for example, HACKING 1983,
p. 208 and BUENO 2011a; but also VAN FRAASSEN 2001, p. 162-163 and
2008, p. 110).
Since van Fraassen aims not only at the acknowledgment of his
position as a coherent alternative to scientific realism (see KUSCH 2015, p.
172), but at making sense of science too (see BUEKENS & MULLER 2012, p.
94 and 99), there is room for alternative proposals concerning the observable/
unobservable distinction, while preserving an empiricist spirit. Van Fraassen’s
notion of observability, in fact, may very well be coherent and meaningful;
however, as Hasok Chang claimed, “his critics are correct when they argue that
van Fraassen’s notion of observability does not have all that much relevance
for scientific practice” (CHANG 2004, p. 85). Alternative proposals can then
be advanced, in case one thinks constructive empiricism can be brought closer
to the actual scientific practice - provided she agrees with Chang, of course.
The aim of this paper, however, is not to propose another
characterization of observability that fits constructive empiricism, but to put
forward a little amendment to van Fraassen’s own antirealism, to the effect that
4
Van Fraassen’s view of science is a version of empiricism - of course, as its name suggests which is meant to be an antirealist stance. Right after presenting it in the first pages of his book
The Scientific Image, in fact, van Fraassen adds: “This is the statement of the anti-realist position
I advocate; I shall call it constructive empiricism” (VAN FRAASSEN, 1980, p. 12) - which
confirms what has been said before: in the philosophy of science, ‘antirealism’ and ‘empiricism’
amount to the same position and are frequently used as synonyms.
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it can actually be seen as a coherent position, albeit controversial, since its
present consistency might be called into question.
Constructive empiricism, observability and observation
Constructive empiricism is probably the most prominent antirealist
view of science nowadays, but it is not the only one. Still, van Fraassen gives
the observable/unobservable distinction such a crucial role - and maintains
such a controversial stand on the issue - that it can be hardly denied that it is
the appearance of his empiricist stance in 1980 what brought back observation
and observability to the center of the stage, in the debate between realists and
antirealists over the last four decades.
What he wrote in 2005, in a paper called “The day of the dolphins.
Puzzling over epistemic partnership”, about what it means to accept a theory
from a constructive empiricist point of view, leaves nothing to the imagination:
“what the sciences say about the observable parts of the world is true, the rest
need not matter. I'm putting this very roughly, but it is enough to make you see
the immediate challenge” (p. 111). The epistemic weight put on the shoulders
of ‘the observable’ is manifestly enormous.
The challenge, of course, includes clarifying what ‘observable’ means. 5
“What I mean by 'observable' here is just what is accessible to the unaided
human senses” (2005, p. 111-112), explains van Fraassen in the same page.
This is in line with both what he has always defended - and reaffirmed in his
last book: “observation is perception, and perception is something possible for
us, if at all, without instruments” (2008, p. 93); and with the ‘rough guide’ of
‘observable’ he proposed in The Scientific Image: “That something is observable
does not automatically imply that the conditions are right for observing it now.
The principle is: X is observable if there are circumstances which are such that,
if X is present to us under those circumstances, then we observe it” (1980, p.
16).
This explains why, according to van Fraassen, celestial bodies such as
the moons of Jupiter or an extrasolar planet are observable (see VAN
5
Van Fraassen ends up putting forward a characterization of observability, in his works albeit in a fragmentary way. His opinion, however, is that it is not a matter for philosophers:
“If anyone wants to frame opinions about just what is observable, I would urge him to draw
on physiology and psychology, and empirical science in general, and not to ask philosophers at
all” (VAN FRAASSEN, 1992, p. 20).
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FRAASSEN 1980, p. 16; and KOSSO 2006, p. 225, footnote 1), while a
paramecium is not (see VAN FRAASSEN 2001, p. 160; and 2008, pp. 105109). As he claims in “Empiricism in the Philosophy of Science” (1985), in
fact, observability presents special limits that are due to the physiology of the
human species (our epistemic community). It is because of them that observable
is an indexical term (to van Fraassen, observable is short for observable-to-us) and
that we cannot admit circumstances in which the constitution of the human
species is modified - as, on the contrary, happens in the 1966 film “Fantastic
Voyage”. There are also general limits, that do not depend on the human
physiology: these are spatial and temporal limits determined by Einstein’s
relativity theory. Interplanetary travels of human crews certainly fit within
these limits and so there is no problem (?) in imagining contexts in which
astronauts are in the vicinity of Jupiter or of an extrasolar planet.
Yet, constructive empiricism depends on a viable distinction between
observables and unobservables, but not on van Fraassen’s distinction: “To
explain my view of what science is, and specifically what is its aim, I need a
feasible distinction between what is observable and what is not”, 6 wrote the
Dutch philosopher in the preface to the Greek edition of The Scientific Image
(2004, p. 1). It is then clear that feasible distinctions other than van Fraassen’s
own one can do the job. Ian Hacking understood this back in 1983: “Imagine a
reader initially attracted by van Fraassen, and who thought that objects seen
only with light microscopes do not count as observable. That reader could
change his mind, and admit such objects into the class of observable entities.
This would still leave intact the main philosophical positions of van Fraassen’s
anti-realism” (HACKING, 1983, p. 208).
Van Fraassen’s own antirealism could not survive a modification in the
scope of the observable, but constructive empiricism might survive it:
What about the observable/unobservable distinction then? The main
points of our discussion are not much affected by just where precisely
the line is drawn. I draw the line this side of things only appearing in
optical microscope images, but won’t really mind very much if you
take this option only, for example, for the electron microscope. After
all, optical microscopes don’t reveal all that much of the cosmos, no
matter how veridical or accurate their images are. The empiricist point is
6
Interestingly enough, back in 1968 Henry Byerly wrote: “If philosophical problems raised by
both phenomenalism and instrumentalism are to be handled, it is necessary to characterize
‘observables’ more perspicuously” (p. 415) - which shows that the issue of observation and
observability has indeed always been a central topic in the philosophy of science.
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not lost if the line is drawn in a somewhat different way from the way I draw
it. The point would be lost only if no such line drawing was to be
considered relevant to our understanding of science (VAN
FRAASSEN, 2008, p. 110).
The point would be lost also in case we concluded that there are no
limits to observability - as some authors sustain (see, for example, MITSUO
NIXON, 2004). But even admitting that, say, electron microscopes produce
visual evidence with the same epistemic status such as that produced by
unaided human perception, the same could hardly be said of the evidence
produced by a scanning tunneling microscope. Such a stand is defended by
Otávio Bueno, a self-declared constructive empiricist, who in 2011 offered “a
way of extending the observable beyond instances of unaided perception, but
which still preserves, within an empiricist view, cases in which certain objects
cannot be observed” (BUENO, 2011a, p. 290). Bueno’s position is a good
example of a version of constructive empiricism apparently closer to the actual
scientific practice than van Fraassen’s own one.
Telescopic and microscopic detections
According to van Fraassen, detection by means of instruments is to be
distinguished from observation, for the latter is unaided (see VAN
FRAASSEN, 2008, p. 93; and CONTESSA, 2006, p. 456). Likewise, he
notoriously prefers considering instruments in general, and microscopes in
particular, as ‘engines for the creation of new phenomena’ rather than
‘windows on an invisible world’ (see VAN FRAASSEN, 2008, p. 96-97; and
KUSCH, 2015, p. 171).
This means that when he wrote that a look through a telescope at the
moons of Jupiter is a clear case of observation, “since astronauts will no doubt
be able to see them as well from close up” (1980, p. 16), he was not really
admitting that it is possible to observe through telescopes - while it is not
through microscopes. As Paul Teller explained, in fact, according to the
originator of constructive empiricism, “what we do with a telescope does not
itself count as observing (…) in the relevant sense” (TELLER, 2001, p. 126).
Whether one can observe through a device such a microscope or a
telescope is, in truth, controversial - at least among philosophers. Martin Kusch
thinks that “the engine-of-creation view is actually shared by constructive
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empiricist and scientific realist” (KUSCH, 2015, p. 172), but this does not seem
to be the case, for there are authors who claim that it is possible to perform
observations through instruments (see, for example, ALSPECTOR-KELLY
2004).
Be that as it may, seeing the result of either a microscopic or a
telescopic detection displayed in a monitor is increasingly common in
nowadays scientific practice. In this case, no one can deny that what scientists
observe is an image7 - and that the instruments have acted as ‘engines of
creation’. How should one deal with such images? Are they veridical?
In the case of microscopes, van Fraassen claims that one is allowed to
keep neutrality with respect to the existence of the entity allegedly represented
by their outputs. In a quite famous passage from his 2001 paper “Constructive
Empiricism now”, the Dutch philosopher challenges the possible parallel with
what is undeniably a picture of a real thing:
If you see a reflection of a tree in the water, you can also look at the
tree and gather information about the geometric relations between
the tree, the reflection, and your vantage point. The invariances in
those relations are precisely what warrant the assertion that the
reflection is a picture of the tree. If you say similarly about the
microscope’s images that they are pictures of e.g. paramecia, then you
are asserting that there are certain invariant geometric relations
between the object, image, and vantage point. But now you are
postulating that these relations hold, rather than gathering information
about whether that is so (VAN FRAASSEN, 2001, 160).
7
An already famous one was released a couple of months ago (April 2019). “The image (…)
showed the edges of [a] black hole - called the ‘event horizon’ - for the first time”
(BORENSTEIN, 2019). In order to produce the now-world-famous image of one of the
largest known supermassive black holes - M87*, located at the center of Messier 87, a massive
elliptical galaxy in the Virgo cluster, 53 million light-years away from Earth - a network of radio
telescopes known as the Event Horizon Telescope was created; the telescopes were
synchronized to focus on the same object at the same time and act as a giant virtual telescope.
“As each telescope acquired data from the target black hole, the digitized data and time stamp
were recorded on computer disk media. Gathering data for four days around the world gave
the team a substantial amount of data to process. The recorded media were then physically
transported to a central location because the amount of data, around 5 petabytes, exceeds what
the current internet speeds can handle. At this central location, data from all eight sites were
synchronized using the time stamps and combined to create a composite set of images,
revealing the never-before-seen silhouette of M87*’s event horizon” (LUTZ, 2019). “It then
took more than a year for that data to be processed into the first glimpse of images that
scientists saw in the summer of 2018” (BORENSTEIN, 2019). We tend to consider a
photograph on a par with an observation, i.e., as warranting (among other things) the belief in
the existence of the represented entity. Does the same apply to the image of M87*? Is it even
adequate to call it a photograph, as newspapers around the world did in April 2019? “There
actually were a few academic holdouts who denied black holes existed, but now they can't, said
Boston University astronomer Alan Marscher, who was on one of four imaging teams”
(BORENSTEIN, 2019). Are scientists actually justified, now, in their belief in the existence of
black holes?
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Kusch explains that, according to van Fraassen, keeping neutrality
about whether a microscopic image is a copy of a real thing or not is “more
illuminating since it allows us to identify realist commitments [as] optional”
(KUSCH, 2015, 172). Such neutrality, however, he then adds, does not prevent
us from gathering information with microscopes. What about telescopes?
If Teller is right and van Fraassen never really meant that one can
perform an observation through a telescope, he then surely considers that in
this case the situation is analogous to that of the reflection of a tree in a pond
- or else what would ‘a clear case of observation’ mean? But even in the case of
the moons of Jupiter, we are in no position (from Earth, at least) to gather
unaided information about the geometric relations between the moons, the
image, and our standpoint - and therefore to claim that the invariances in those
relations warrant the assertion that the image is a picture of, say, Ganymede.
The possibility of triangulating or comparing the entity represented by
the image with the real one is only hypothetical and may never become reality.
It seems more a logical/theoretical possibility than an actual one and relying on
such an argument to defend a realist interpretation of the image produced by a
telescope might not warm many people’s hearts.
In the face of this, one might then want to modify the general limits of
observability so that extrasolar planets and other celestial bodies are not
classified as observable anymore (as happens with any object outside our light
cone) and thus their observability status cannot be invoked to guarantee that a
look at them through a telescope is a clear case of observation - whatever that
means.8 However, such a move would not solve the problem, for the very same
situation can arise with terrestrial entities:
do we or do we not observe foxes in pitch darkness using an infrared camera? One might answer 'Clearly, yes' (denying that there is any
vagueness), on the grounds that if there were adequate illumination
we could see the foxes with unaided vision. But since the illumination
is not actually adequate, it can only be our confidence in the camera
which backs our belief in this counterfactual, and, if it is a vague
matter how far instruments can expand the domain of the genuinely
observable, it will be an equally vague matter when this confidence is
justified (MENUGE, 1995, p. 61).
8
Note that such an argument would not apply to any telescopic detection, for in many cases it
is actually possible to triangulate and make a comparison with the real entity. This happens, for
example, when one takes a look at our Moon through a telescope.
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Leaving aside the question of whether it is possible to observe through
an instrument or not, Angus Menuge’s argument can be evoked to question
van Fraassen’s appeal to the observability status of an entity in order to
support the belief that the image which represents it is veridical.
Still in 1982, Philip Hanson and Edwin Levy, authors of one of the
first reviews of The Scientific Image, wondered why there should be a difference
between accepting a theory about the moons of Jupiter - that van Fraassen
considers observable, but that have never been observed directly - and one
about bacteria - which belong to the class of the unobservable, since they can
only be detected by means of a microscope. According to the two
philosophers, statements about the moons of Jupiter or about bacteria are
close to being evidentially on a par, for it is not clear “how the fact that we
could in principle observe some objects directly gives greater evidential warrant
to statements about such objects” (HANSON & LEVY, 1982, p. 291). 9
Hanson and Levy talk about statements, of course, but one might want to say
that what goes for statements goes also for pictures of entities like bacteria or
celestial bodies.
It is worth remembering another criticism along the same lines, made
by Peter Kosso in the past decade and directed against van Fraassen,
concerning the detection of extrasolar planets (ESPs):
The constructive empiricism of Bas van Fraassen would classify ESPs
as observable, on the grounds that a human being in the right place
could see them with the naked eye. But this kind of externalist
epistemology, allowing justification to rely on unavailable information
(we are not in any position to see ESPs with the naked eye) is
unhelpful in deciding which particular scientific claims warrant belief
(KOSSO, 2006, p. 225, footnote 1).
Appealing to the observational status of the entity represented by a
certain picture seems to be a very weak criterion, not capable of justifying the
belief in the veracity of the image, and should probably be rejected - unless
one does actually compare it with the real entity, as in the example of the
reflection of a tree in a pond. Are there other criteria, capable of supporting
9
Still in 1982, Paul Churchland made a similar comment: “I (…) fail to see how van Fraassen
can justify tolerating an ampliative inference when it bridges a gap of spatial distance, while
refusing to tolerate an ampliative inference when it bridges a gap of, for example, spatial size”
(CHURCHLAND, 1982, p. 276).
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van Fraassen’s selective confidence in the images produced by the instruments
used in science and acceptable to the originator of constructive empiricism?
Buekens’ criterion
“Observing in a space of reasons” is a manuscript originally written by
Filip Buekens in 1996 (revised in 1999), and that is circulating in the
philosophy of science community ever since.10 In the paper, Buekens stresses
the importance of being able to identify an object from different points of
view, so that it can be considered observable. Following Christopher Peacocke,
who summarises P.F. Strawson’s and Gareth Evans’s views on what counts as
an observable object, Buekens endorses a criterion almost ‘tailor-made’ for van
Fraassen:11
It is crucial to our conception of an observable object that it be the
centre of a perceptual polygon - it can be perceived or observed from
different angles (when the observer moves) and remain observable
when it moves in space. (…) It comes with our concept of an
observable object that it can be observed - identified - to be that object
from different perceptual angles. The observer must be able to place
it at the centre of a perceptual polygon. The ‘able’ in ‘observable’
partly depends on whether this condition can be fulfilled. The angles
of the polygon are locations in space from which the observer is able
to identify the object as it moves in space, or as he moves in that
space (BUEKENS, 1999, p. 26).
According to Buekens, microscopic entities cannot be placed at the
center of a perceptual polygon, for there is only one perceptual angle from
which we have access to them, namely, the one provided by the instrument.
Hence, they are not observable - note that there is no mention to the reliability
of the instruments here. Following the same criterion, on the other hand, one
is allowed to classify the moons of Jupiter as observable, since they can be
perceived from different points of view - and because we can keep track of
them as they move in space. 12 The same goes for anything that can be detected
10
“Observing in a Space of Reasons” could originally be found in Buekens’s page on Tilburg
University’s website. A new version of it (but with a different title), that dates 2005, was kindly
sent to me by Professor Buekens in 2013. In an e-mail message of 28 October 2013, he
authorized citing both 1999 and 2005 (unpublished) versions.
11
The argument van Fraassen presents in “Constructive Empiricism now” seems to be
inspired in this criterion, but there is no mention to Buekens in the paper.
12
Keeping track of the object of perception is (quite obviously) considered as a characteristic
and constitutive feature of observation (see, for example, GHINS, 2005, p. 96).
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through a telescope.13 Is van Fraassen’s different treatment of the outputs of
microscopes and telescopes finally backed up?
Unfortunately, Buekens’s conclusions do not seem to apply to the case
of the paramecium (and of many other microscopic entities). As a matter of
fact, this microorganism can be perceived or observed from different angles,
when the observer moves, and remains observable when it moves in space.
Contra Buekens, it is therefore possible to say that the paramecium can actually
be placed at the centre of a perceptual polygon. It is not true that we have only
one angle from which we have access to it, despite this being provided by the
instrument. Paramecia do satisfy Buekens’s observability criterion.
Moreover, in the passage above Buekens implicitly admits the
possibility of performing observations through instruments. It then becomes
clear why van Fraassen almost ignored the criterion presented in this section. 14
It is not ‘tailor-made’ for him, as perhaps Buekens thought it was. If one wants
to defend van Fraassen’s antirealism, Buekens’s criterion is actually of no help.
What then?
In The Scientific Image van Fraassen wrote: “Seeing with the unaided eye
is a clear case of observation” (p. 16) - which is unquestionable. A few lines
further on, still in the same page, he added: “A look through a telescope at the
moons of Jupiter seems to me a clear case of observation, since astronauts will
no doubt be able to see them as well from close up”. In line with van
Fraassen’s idea that “the language of science must be literally understood”
(VAN FRAASSEN, 1980, p. 11), one might then be tempted to interpret in a
literal way the above claim about telescopic detections (of the moons of
Jupiter, at least) - which seems a quite natural thing to do - and judge that,
according to the originator of constructive empiricism, it is actually possible to
observe even when one uses a telescope - while the same is not possible with a
microscope.
“Since we can’t see things that don’t exist” (VAN FRAASSEN, 2001, p.
158), this argument would give a robust support to a realist interpretation of
13
This is why it has been said that the criterion put forward by Buekens seems to be ‘tailormade’ for van Fraassen.
14
“Observing in a Space of Reasons”, in its 1996 version, is marginally mentioned by van
Fraassen in his 2002 book The Empirical Stance.
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an image produced by a telescope - and to van Fraassen’s dichotomic attitude
with respect to telescopes and microscopes. However, there is a clear petitio
principii here, for claiming that it possible to perform an observation through a
telescope because the detected entity is observable is obviously circular. If one
wants to sustain that telescopic detections are observations, other reasons must
be put forward.15
As is well known, Galileo Galilei defended the veracity of the
detections made by means of his cannocchiale on the grounds that through it one
could also observe familiar terrestrial entities. Why should it deceive us when
aiming the instrument at celestial bodies? Now, while it is quite natural to agree
with the father of the scientific method and reject his opponent’s famous
counterarguments, van Fraassen would not be too happy with such a line of
reasoning, for the above argument is notoriously used to support a realist
interpretation of microscopic detections too:
Examples of overlap arguments are familiar to all of us. We trust
what we see through a low-powered telescope because its domain of
applicability overlaps what we can see with the naked eye, and within
the visual domain the telescope reproduces accurately, precisely, and
with good resolution familiar features of the world. I see my wife on
the plain over yonder, and when I train the telescope on her, there
she is again, simply larger and clearer. I can just see the fruit fly on
the microscope slide - I put it under the low-powered microscope
and here it is; I can see the head in much more detail through the
greater resolution of the microscope (HUMPHREYS, 2004, p. 18).
Here is a picture that shows how the overlap argument can be used to
justify a realist interpretation of the detections performed with an electron
microscope - and how microscopes are actually calibrated against each other:
15
A couple of decades ago, Jesús Mosterín made the following comment: “We do not have at
our disposal any satisfactory philosophical account of the notion of observation which fully
incorporates its technology-mediated character in modern science” (MOSTERÍN, 1998, p. 73).
It is not clear that the situation has changed since then - provided one agrees that observation
can be technology mediated, of course.
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Figure 1. The resolving power of various microscopes, with representative objects
within range for both light microscopes and electron microscopes. Source: <https://
www.thermofisher.com/br/en/home/life-science/cell-analysis/cell-analysis-learningcenter/molecular-probes-school-of-fluorescence/fundamentals-of-fluorescencemicroscopy/epifluorescence-microscope-basics.html>
Of course van Fraassen would not be willing to accept such an
argument as a justification of the belief in the veracity of the output of an
imaging instrument, on pain of having to admit that bacteria are observable
too - and thus jeopardizing his own antirealism.16
Alternatively, a quite obvious way of supporting a realist interpretation
of the use of the telescope is by appealing to the reliability of the instrument;
but of course the same argument can also be invoked by the supporters of a
realist interpretation of the use of the microscope - not to mention that
geometrical optics is the theory behind the construction of both optical
telescopes and light microscopes. The same happens in case one wants to rely
on a counterfactual argument such as the one Bueno put forward in 2011
16
Unless he maintains that while such an argument works for telescopes, it does not in the
case of microscopes; but it is very unlikely that van Fraassen would make such a claim.
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(Bueno actually uses it to defend a realist interpretation of the use of most
kinds of microscopes!):
(i) Had the scene before our eyes been different (within our cognitive
device’s sensitivity range), our perceptual experience would have been
correspondingly different. (ii) Had the scene before our eyes been the
same (within our cognitive device’s sensitivity range), our perceptual
experience would have been correspondingly the same (Bueno 2011a:
278, our translation).17
In sum, it seems that when it gets to interpreting the function of
telescopes and microscopes, these instruments are actually on a par: any
argument one puts forward in support of a realist interpretation of the use of
the first - meaning here either the admission that it is possible to observe
through them or the claim that their outputs are veridical - can also be invoked
to support a realist interpretation of the use of the latter. The only exception
seems to be van Fraassen’s appeal to the observability status of the detected
entity, which should allow for a different treatment of telescopes and
microscopes. This argument, however, only works when there is an actual
comparison between what is detected and the real object (or between the
image produced by the instrument and the real object); 18 otherwise, the line of
17
See also Noë (2003, p. 94-97) and, for a version of these counterfactual conditionals specific
for microscopes, Bueno (2011b, p. 256). Note that here Bueno clearly admits that perception
can be instrument mediated - such as happens with Bueken’s criterion. As said before, this
should allow to extend the observable beyond instances of unaided perception; and yet, within
an empiricist view, there should be cases in which certain objects cannot be observed (see
BUENO, 2011a, p. 290). According to Bueno, in fact, “not only should perception offer a
reliable information generation process, but it must be such that one knows that the process is
indeed reliable; or, at least, we should have access to the factors sustaining its reliability”
(BUENO, 2011a, p. 281, our translation). This internalistic requirement should ensure that a viable
distinction between observable and unobservable will always exist, for in cases such as that of
the scanning tunneling microscope it is not obvious at all that one can know that the relevant
counterfactual conditions are satisfied; therefore, maintaining an agnostic attitude in this case is
perfectly legitimate. Salve, van Fraassen!
18
A quarter of a century ago, remote sensing was a quite new discipline. From it, William
Seager borrowed the locution ‘ground truth’, which fits relatively well what has just been said:
“The term ‘ground truth’ comes from the relatively new and, I am told by some, faintly
disreputable discipline of Remote Sensing. Satellite or aircraft images of both observable and
unobservable features of the earth can be formed through a variety of techniques such as x-ray
imagery, infrared imagery, side-scan radar and the like, and these are said to reveal important
more or less large-scale terrestrial phenomena. The interpretation of such images is not
straightforward, though they do give every appearance of imaging something. Let's say that an
infrared image of a field shows up certain ‘patches’ of diseased potato plants, revealed as such
by the color of these patches in the infrared image although this is ‘false color’ of course,
selected by film technicians, since we don't see infrared (…). We know that such images are
reliable because we have obtained ground truth: somebody, sometime, went to see just what
corresponded with what in an infrared image of a real field of potatoes” (SEAGER, 1995, p.
469).
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reasoning is too weak - or even circular, in case one maintains that a detection
performed through a telescope is an observation.
No way out for van Fraassen’s selective antirealism then?
Conclusion: did van Fraassen pick an unnecessary fight?
In the previous sections we have seen that, according to Kusch, in
discussions about the function of instruments in science, the engine-ofcreation view is shared by constructive empiricists and scientific realists (see
KUSCH, 2015, p. 172). Since it was van Fraassen who put forward this view,
Teller explained that for a constructive empiricist a look through a telescope
does not count as an observation in the relevant sense (see TELLER, 2001, p.
126), notwithstanding the fact that the originator of this antirealist stance
wrote that it is a clear case of observation (see VAN FRAASSEN, 1980, p. 16).
Still, van Fraassen does not consider that the situation is the same as
that of a paramecium detected via a microscope, for in the case of this
protozoarium we cannot empirically investigate the geometrical relations
between the eye, the microscopic image and the postulated unobservable
entity. “For the constructive empiricist this is the difference that makes all the
difference: since we are unable to study the geometrical relations between
empirical and postulated entities, we are entitled to suspend belief in the latter”
(KUSCH, 2015, p. 172).
In case one detects the moons of Jupiter through a telescope, on the
other hand, she can in principle compare the instrumental detection with the
real entities, “since astronauts will no doubt be able to see them as well from
close up” (VAN FRAASSEN, 1980, p. 16). Now, if the truth be told, van
Fraassen has never clarified his position on telescopic detections, but it seems
quite straightforward that to him microscopes and telescopes are not a par,
since in the first case it is not possible to compare the instrumental output with
the entity allegedly detected, while in the second it is, at least in principle again, were this not the case, what on earth would ‘a clear case of observation’
mean then (and, especially, why adding that it is so since astronauts will no
doubt be able to see the moons of Jupiter as well from close up)?
As discussed before, however, appealing to the observability status of
the detected entity, in order to establish whether an instrumental output is
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veridical or not, is a very weak criterion - if not wrong, for it has ‘a circularity
flavor’ - and should be rejected. Again, Kusch stresses the importance of
“reading the results of science in a way that is neutral with respect to the
debate between scientific realist and constructive empiricist” (2015, p. 180).
Why should this be the case only when it gets to microscopes?
Perhaps the neutral way to read the results of science with respect to the
debate between scientific realist and constructive empiricist entails interpreting
realistically the outputs of a telescope, for this seems to be a position actually
shared by the common-sense-realist van Fraassen 19 and his opponents.20
Therefore, if “van Fraassen is entitled to demand that the scientific evidence
be rendered in a neutral way, and that this neutral way is precisely the
constructive-empiricist interpretation” (KUSCH, 2015, p. 180), one might
think that the veracity an image of the moons of Jupiter is not a topic in hand.
However, Kusch focuses only on microscopes because his aim is to
defend van Fraassen’s view on these instruments in particular, but in the same
paper he acknowledges the possibility of maintaining a neutral attitude with
respect to telescopic detections:
Note also that our readiness to speak of ‘seeing’ in the case of, say,
the Hubble Space Telescope (HST) or the Scanning Tunnelling
Electron Microscope (STEM) is rather unstable (…). Upon first
encountering images produced by the HST or the STEM most ‘naïve’
subjects are indeed happy to speak of the HST allowing us to see very
distant objects in the universe, or the STEM enabling us to observe
nanoscale objects. And yet, the naïve subjects’ willingness to speak of
seeing and observing in these cases is easily disrupted. Once the
subjects learn how the images are produced, and how much
computer enhancement is involved - e.g. all the colours are computer
generated - they begin to withdraw terms like ‘seeing’ and ‘observing’
(KUSCH, 2015, p. 178).
The same, one might add, happens with the images produced by
telescopes, such as the one that has recently become known as ‘the first photo
ever captured of a black hole’. Once the subjects learn how the image has been
produced,
21
and how much computer enhancement is involved - e.g. all the
19
“I try to be an empiricist, and as I understand that tradition (what it is, and what it could be
in days to come) it involves a common sense realism in which reference to observable
phenomena is unproblematic: rocks, seas, stars, persons, bicycles…” (VAN FRAASSEN,
2008, p. 3).
20
In this paragraph, ‘constructive empiricist’ should then be read as meaning ‘van Fraassen’.
21
“Astronomical observations often take place in astronomical observatories, but nowadays
the telescopes in the observatories lack eye-pieces for direct observation by the astronomer.
Instead, nitrogen or helium refrigerated CCDs occupy their place. The astronomers are in a
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colors are computer generated - they will probably begin to withdraw terms
like ‘photograph’ and ‘veridical’.
I will then borrow another passage from Kusch’s work and suggest
that a second idea for motivating the coherence of an agnostic stance with
respect to the outputs of a telescope is based on the fact that the engine-ofcreation view is, according to the Austrian philosopher, actually shared by
constructive empiricists and scientific realists. “Van Fraassen suggests that we
do not need to go beyond this common baseline. We might think of the
microscope image as a copy of a real thing, invisible to unaided perception, but
‘…it is accurate and in fact more illuminating to keep neutrality in this
respect…’ (2001, 155; 2008, 109). It is more illuminating since it allows us to
identify realist commitments [as] optional” (KUSCH, 2015, p. 172).
Accordingly, I claim that we might think of the telescopic image of a
black hole or of an extrasolar planet as a copy of a real thing, invisible to
unaided perception (from Earth), but it is accurate and in fact more
illuminating to keep neutrality in this respect - unless one does actually
compare the telescopic detection with the real entity. Such neutrality does not
prevent us from gathering information with telescopes. “And it does not
prevent us from focusing on the regularities in the phenomena that Hacking
too rightly stresses” (KUSCH, 2015, p. 173).
Saying that a look through a telescope is an instance of observation is
clearly at odds with the claim that observation is unaided perception. But
maintaining that the output of such an instrument is a faithful representation
of a real state of affairs on the grounds that it is in principle possible to
compare the produced image with the represented entity (or entities) does not
seem to be an acceptable criterion either. In most cases, in fact, as said before,
it seems more a logical possibility than a physical possibility. Think of the
exoplanet Beta Pictoris b, for instance. Will a human being ever be capable of
directly observing a planet which is 63 light-years away from Earth? I do not
think so.
One might quite rightly say, then, that an extrasolar planet and a
paramecium are actually “close to being evidentially on a par” (HANSON &
separate room and watch the screens of their computers (…).What the astronomer sees on the
screen has gone through multiple transductions of photons into electric charges and currents,
and electronic transformations inside the computer, till finally the last electrons are transduced
back to photons in the cathode ray tube of the computer screen” (MOSTERÍN, 1998, p. 70).
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LEVY, 1982, p. 291) and that, being so, telescopic images should receive the
very same treatment van Fraassen grants to the microscopic ones. Unless one
does actually compare the output of a telescope with the part of the real world
depicted in it (remember Seager’s ‘ground truth’), it is accurate and in fact
more illuminating to keep neutrality with respect to the claim that the image is
a copy of a real thing. As in the case of the microscopes, it is more
illuminating since it allows us to identify realist commitments as optional.
“As constructive empiricism has it, there is nothing incoherent in the
thought that we find out by inference, not observation, ‘how unobservable
things are’ (where ‘unobservable’ means unobservable by our naked eyes)”,
says Kusch (2015, p. 179). In most cases of telescopic detections, the situation
is exactly that described by the Austrian philosopher. There is nothing
incoherent in the thought that we find out by inference, not observation, ‘how
extrasolar planets are’, for example.22
Moreover, it is my contention that even if van Fraassen admitted that it
is accurate to keep neutrality - and thus that realist commitments are optional also in the case of the images produced by telescopes, his antirealism would
not be affected. If observation is unaided perception, a telescopic detection
makes no difference at all for the observability status of the detected entity (or
entities). Being so, it does not affect the constructive empiricist’s belief in the
existence of extrasolar planets and the like either.
This also means, however, that an image of an exoplanet cannot
guarantee that the depicted celestial body exists and therefore cannot justify
the related belief; it can only offer, at most, Popperian-style corroboration. On
the other hand, if van Fraassen kept a neutral attitude with respect to the
outputs of a telescope, such as he does with the microscopic ones, the present
consistency of his antirealism would not be called into question, for it would
not be resting upon an objectionable criterion - that an instrumental detection
is on a par with an actual observation, when the detected entity is an
observable (which is what it means to claim that a look through a telescope at
22
One might think that the observability status of the celestial bodies strengthens the
inference, in the case of telescopic images; and so that there still is a difference with the images
produced by a microscope. I would find this questionable, for the reasons seen in this work
(see Kosso’s argument, for example); but, admittedly, it would be less ‘compromising’ than
using this same argument as a justification for the belief in the veracity of the telescopic
outputs.
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the moons of Jupiter is a clear case of observation since astronauts will no
doubt be able to see them as well from close up).
In conclusion, van Fraassen might have picked an unnecessary fight,
with his claim about the telescopic detection of the moons of Jupiter. As a
matter of fact, whichever way one interprets his branding such a detection as ‘a
clear case of observation’, serious objections may arise. Perhaps a more modest
attitude, like acknowledging that the assertion of the veracity of an
instrumentally-produced image can only be vindicated by a comparison with
the real state of affairs (even in the case of nocturnal foxes and other
‘Menuge-like’ situations), could prevent this from happening. Van Fraassen’s
own antirealism would easily survive this admission and the originator of
constructive empiricism could avoid the eventuality of being charged with
applying double standards with respect to instrumental outputs.
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21