Draft
NON-NAÏVE DIRECT REALISM
Summary:
This short paper aims to answer the main arguments
against direct realism. It is based on two theses: that of the Janus face of
perceptual experience, and that of the cognitive primacy of sensory content
(sense data). Together they help us give better answers to the old arguments of
illusion and of science against direct realism.
Key words: direct realism, sense data, argument of illusion,
philosophy of perception.
My intention here is to show that we can reconcile direct realism with the idea that we in
some way perceive the external world through a “veil of sensations” (of sense
data). It is difficult to say something really new about the classical
philosophical problem of perception. Aware of this, my goal here is to
highlight some points in defense of a “non-naïve” direct realism.
1.
Janus Face thesis of perceptual experience
My understanding of direct realism is grounded on two
theses. I can state the first now: everything experienced in normal perception
has a kind of Janus face. That is, we can conceive the phenomenally given in
sensory-perceptual experience of the outside world in two different ways (Costa
2018, 419 f.):
(A) As the psychological experience of cognitively
dependent internally given sensory
contents (more often called sense
data).
(B) As the proper perceptual experience of
cognitively-independent, externally given perceptual
contents (understood as physically singularized entities).
Psychological experience (A) gives us what we may call
sensory impressions or contents (also called sense data, sensations, sensa,
qualia, ideas, phenomena…). Today it is beyond doubt that sensory contents are
always present in perceptual experience. Although in the past many philosophers
denied the existence of sensory contents (understood as sense data) as those
sensory contents given in (A) as necessarily accompanying proper perceptual
experience (B), I defend the view that today the issue has been definitively settled
by neuroscience, at least regarding visual experience. The computational
reconstruction of moving mental images taken with BOLD fMRI by reading brain
activity first made at the University of Berkeley was able to show moving
visual images formed in the brain when a person sees objects or watches a film
(Gallant et al. 2016). After experiments like these, who would dare to doubt the
existence of sense data accompanying perception?
However,
thesis (B) also seems beyond doubt: it is the idea that in addition to sensory
experience, when we perceive something, this something is given to us as an
external entity. Indeed, it is also a commonsense truth to say that we usually
perceive the external world as it really is, constructed of mind-independent
entities like material objects and their singularized properties.
The clearest
evidence favoring this double view is tactile experience (Cf. Searle 2015: 24). Suppose I touch a hot stove with my hand. I
can say I have a sensation of heat: this sensory-impression is the
psychological internal sensory-content of experience (A). Alternatively, and
correctly, I can also say that I have perceived that the stove in itself is
hot; this is the correct perceptual experience of the externally given physical
entity (B). The essential to be noticed in this example is that in the normal
case we are unable, as John Searle would note, to phenomenally distinguish experience (A) from experience (B). The
content seems to be the same, though differently understood. Thus, in a similar
way I can say:
(A) [I feel that] I am holding a tennis ball in my
hand.
(B) I am
holding a tennis ball in my hand.
Now, of auditory experience, I can say:
(A) [I have the auditory impression that] I hear
thunder.
(B) I hear
thunder.
And of the most common visual experience, I can also
say:
(A) [I have the visual impression that] I am seeing a
fishing boat entering the mouth of Pirangi River.
(B) I am seeing a fishing boat entering the mouth of
Pirangi River.
As you can see, the phenomenal descriptions outside
the brackets are the same, but in the (A) cases, I speak of sensory contents
occurring in my head (sense data), while in the (B) cases, I speak of
independent factual contents pre-existing in the external world. The real thing
(B) is cognitively dependent on sense impressions (A), since without (A) I
couldn’t know (B). On the other hand, sense impressions (A) are causally
dependent on (B), which causes (A). These conclusions lead us to our second
thesis.
2.
Thesis of the cognitive primacy of sensory content
Along with the thesis of the Janus face of content in
the case of real perception, I will defend the epistemic thesis of a cognitive primacy of sensory content.
The conditions in which sensory content or sense data can be interpretatively
resituated as perceptual content are the conditions in which sensory content is
a medium through which perceptual content can be given by us. This thesis of
cognitive primacy of sensory content can be complemented with a thesis of the causal primacy of perceptual content in
the case of real perception, which is its ontological counterpart.
I can
illustrate how harmless the above duplicity is by comparing it with the kind of
doubling that occurs in our interpretation of objects we see in a mirror. What
we see in a mirror can be interpreted as: (A’) a simple image of things, for
instance, the image of a vase of flowers on a table. But it can also be seen
as: (B’) the vase in itself that I am seeing in a mirror. For instance, I can
point to an object I see in a mirror, and you can ask me if I am pointing to
the reflected image of the vase of flowers or to the real vase of flowers
behind me. That they belong to different domains is made clear by functional
differences: the image isn’t considered real, because it has a changeable size,
we cannot touch, smell or break it. The real vase of flowers, on the other hand,
has an unchangeable size, and can be touched, smelled, directly seen from all
sides, manipulated, broken, etc.
However, by looking at the mirror, we would
not be able to see the vase on the table without the help of the image; and the
elements and relations between both will coincide, at least partially. As in
the case above, (B’) is cognitively dependent on (A’), because without the
image (A’) you couldn’t see (B’). Alternatively, (A’) is causally dependent on
(B’). This is why when you pay attention to an object in a mirror you see it as
perceptually dependent on its image, but when you pay attention to the image,
you see it as causally dependent on the real object. You can easily say that
you see the reality through the image.
But you will never say that you cannot see the vase only because what you
really see is only its image. Moreover, you can also say that you are seeing
the real vase directly by means of
its image, at least if you compare it with the same vase seen in a photo or a
picture. You can see either the real vase or its image – but not both together.
And the mirror-image also shows that our experience is perspectival. What we
see are typically facets, aspects.
The analogy
shows how we pass from the mind-dependent to a mind-independent interpretation
of phenomena. We can observe an external factual content by means of its
phenomenal experience as involving a purely sensory content, which is internal.
The phenomenon of post-images illustrates the point clearly: after looking at
the sun very briefly one can close one’s eyes, and the image of the sun does
not disappear immediately. As we will see, the dichotomy considered above is
also important because it is a condition for the defeasibility of observational
evidence: it allows us to explain why evidence can deceive us.
Beyond the
analogy, we can consider the case of the contextual differences between sensory
experience and perceptual experience. When we compare sensory content with perceptual
content, we can see that here there are also clear conditions to distinguish the
first from the second. Together these conditions, which were already listed by
philosophers like Descartes, Locke, Hume, Kant, Frege, and G. E. Moore, form what
we could call the reality criterion (Cf. Costa 2018; 435-6). Based on them I
can conceptualize the reality criterion as the conjunction of the following
four conditions for the diagnosis of external reality. The first two are
conditions of externality and can be spelled as:
1.
The
content must be given independent of our will,
2.
The
content must be capable of being object of interpersonal agreement under
suitable circumstances.
The second two conditions constitutive of our
criterion of reality are the following conditions of reality:
3.
The
content must be given to us in its most intense degree and detail, and often in
co-sensorial modus.
4.
The
content must obey the laws of nature, it must display expected regularities of
different forms, must be also contextually coherent.
Once the phenomenal content given to experience satisfies
these four conditions conjunctively,
we are usually[1]
allowed to interpret the content as being “the real thing”: an externally given
perceptual content, that is, an object, a singularized property (trope), an
event, a state of affairs, a process... It is fundamental that the satisfaction
is conjunctive, since when satisfied separately, these criteria can be only
symptoms[2]
unable to warrant external reality (there are intense hallucinations, there are
ways of controlling external reality using only the activation of the motor
cortex, interpersonal hallucinations are possible under the influence of drugs,
a very tedious dream can display usual regularities…). When a person has a
dream, the person has sensory content without perceptual content. In a dream usually
only condition (1) (of externality, it seems external) is satisfied. In the
case of alcoholic hallucinosis not only condition (1) but also condition (3) (the
images seem to be quite real) is satisfied, though not (2) and (4). We can say
that in usual circumstances the satisfaction of the criterion of reality simply
defines what is externally real. On
the other hand, before the computational reconstruction of brain images, the
thesis that sensory content exists, acting like a medium to be projected on the
real world in real perception could be more easily contested.
As in the
case of mirror images, the perceptually real content inferred from the conjunctive
satisfaction of conditions (1) to (4) is cognitively (epistemically) dependent
on pre-existing sensory content, which does not conjunctively satisfy conditions
(1) to (4), but does satisfy criterial conditions for sense data, like that of
being susceptible to the computational imagistic reconstruction of brain
activity. And also in the same way as in the case of mirror images, sensory
content can be shown to be causally (ontologically) dependent on pre-existing
external perceptually real content (which does conjunctively satisfy conditions
(1) to (4).
3.
Response to the argument of Illusion
There are, however, two traditional arguments designed
to show that the kind of direct realism suggested above must be wrong, and it
is advisable to answer them here. They are the famous argument of illusion and
the argument of science.
I begin with the famous argument of illusion.
It usually concerns cases of perceptual illusions in which what we think we
perceive is not what we should perceive, particularly in the extreme case of
hallucinations in which we only imagine we perceive something. The main goal of
the argument of illusion is the replacement of direct realism by indirect realism, according to which we
perceive the objectively real world indirectly through the “veil of sensations”
constituted by sensory perceptions or sense data.
There is an
extensive philosophical literature aiming to show that the argument of illusion
is fallacious, and we do directly perceive things around us as they really are.
In my understanding of direct realism, I do not wish to deny that there are
sensory impressions or sense data. I do not even wish to deny that we perceive
the world through a “veil of sensations” or sensory perceptions or sense data,
since by accepting (A) I have accepted these conclusions. What I reject is the
claim that these things make our perception indirect, which is the basic claim
of indirect realism. For we never say we perceive our sensations; what we might
say is that we perceive the world directly through, or by means of, or by a
contextualized interpretation of what we receive as our sensations or sensory
impressions. This suggests that the fact that we can show we perceive the
external world through a “veil of sensations” doesn’t make our perception of
the external world indirect, and it is a category mistake to defend this view.
Put simply: the central problem with the argument of illusion is that it is
based on a misunderstanding of the semantics of our concept of being direct. Consider the following two sentence pairs:
1. The trip is direct (the bus travels directly from
Constance to Munich with a lunch stop of thirty minutes).
2. The trip is indirect (first you take a bus from
Constance to Lindau, then a train to Munich).
1. The bullet struck the victim directly (after
piercing window glass).
2. The bullet struck the victim indirectly (after
ricocheting off a wall).
These examples show that what makes some relations
direct is not necessarily the fact that we cannot find intermediaries between
the relata – they very often exist
and there can be more than just one. Directness/indirectness is an essentially
conventional distinction that depends on the relevance of the intermediaries
for what we aim to consider.
In the case
of perception, conventions allow us to say that we perceive things around us
directly, even if by means of causal processes involving a number of
intermediaries. And there is nothing wrong in accepting the view that we
perceive things directly by means of sense data or through a “veil of
sensations,” just as much as there is nothing wrong in saying that the victim
was struck directly by a bullet, though it first had to go through window
glass.
Having in mind what I just said, I will consider
only a few well-known examples of the argument of illusion, showing where they
fail to prove that perceptual experience is indirect:
EXAMPLE 1: If with closed left eye I press the side of
my right eye with my right finger, I have the impression that things in front
of me move in the opposite direction. Consequently, what I see directly are
only images of things, that is, sensory impressions, and not things as they are
in themselves.
ANSWER: Even if I show by pressing my eye that I see
things moving through my visual field, this does not mean that I am not seeing
the things directly. In fact, I can even say, ‘I see external things directly
and precisely as they are, although they seem
as if they were moving.’
EXAMPLE 2: If I hold my index finger fifty centimeters
from my face and look at the other end of the room, I see two images of index
fingers when focusing on the far wall. If I then focus my eyes on the finger,
the two images merge into a single image. Since they are not phenomenally
different in the two cases, I conclude that what I really see are sensory
impressions of my index finger, even if I can locate my finger through these
sense data.
ANSWER: As Searle has noted, I can instead say, ‘I do
not see two fingers… I am directly seeing my index finger as if it were doubled.’
EXAMPLE 3: I look at a coin that I am holding at an
angle. I know it is round, but it appears elliptical. Indeed, only occasionally
do I see a coin with a round form, which is called its real form. So, what I
primarily see are my sensory impressions.
ANSWER: About the form of the coin, it appears
elliptical, but I can say that I directly see a round coin that only looks elliptical because it is
being held at an angle. – As A. J. Ayer noted, what we consider to be real is
often a question of convention (Cf. Ayer 1973, Ch. 4). We have the
convention that the real form of a coin or a table is the form we see when we look
at them from above. In the same way, we have a convention that the real form of
a mountain is the form we see when looking at it from the ground below it at a
distance, but not an aerial view from above (e.g., Matterhorn, Sugarloaf). The real color of a tropical mountain
is normally green, even if it may seem blue when viewed from a great distance,
etc.
EXAMPLE 4: Suppose I have a perfect hallucination of a
white horse. What I see is not a real white horse, but only a hallucinatory
image. Since this image made of sense data isn’t different from what I see when
I see a real white horse, the primary object of perception must be my sensory
impressions or sense-data.
ANSWER: Finally, in the case of a hallucination, it is
simply wrong to say that I see the content
of my hallucination. I only believe I see it, when in fact there is nothing
there to be seen! Verbs like ‘seeing,’ ‘perceiving,’ ‘being aware of’ are
primarily related to the factual, objective content, and not to a merely
sensory content. Even if it is through sensory content that we have perceptions
of things, this does not make our realism indirect. In a similar way, when we
say that a bus made a stop of thirty minutes for lunch, this does not mean that
the bus trip was indirect.
Summarizing: we perceive things directly, even under
misleading conditions like those of delusions, which justifies the direct
realist view of whatever is given in perception. Nor does this means that there
cannot be an irrelevant veil of sensory impressions or sense data in-between,
being interpretatively relocated as constituents of objective reality. This
justifies my psychological interpretation (A) of a given content as based
merely on sensory data, without forcing me to reject interpretation (B).
4.
Response to the argument of science
Finally, a word about the argument of science.
According to this argument, perceptual experience depends on the stimulation of
distal neuronal cells that in the end leads to the stimulation of cortical
regions in the brain. In the visual case, as far as I know, it seems that what
we call sensory impressions or sense data has much to do with the activation of
the striate cortex, because the stimulation of this region without the
activation of photoreceptors in the retina is apt to produce hallucinatory
phenomena (Teeple, Caplan, Stern 2009: 26-32). The conclusion of this argument
is that our experience is in fact the experience of something occurring in our
brain, which is nothing but the experience of sensory impressions or sense
data. Consequently, our direct experience can only be one of these sensory
impressions occurring in our brain. From this it should follow that we cannot
have a direct experience of the world around us; it also follows that we cannot
have any warrant that our contents of experience reflect the way the external
world really is. We cannot even be sure of its real existence. Worse yet, we
may be led to the incredible conclusion that since our brain also belong to the
external world, we cannot even be sure that our brain exists... All we can be
sure of is that there are all these changing flocks of sensory impressions!
The answer to the argument of science is that
there is nothing semantically wrong in saying that we directly experience
things given in the external world, even if this experience requires underlying
neuronal work as intermediary means. In the case of visual perception, the
relevant point is that the sentence ‘I directly see the object’ belongs to our
ordinary language, while expressions like ‘by stimulating of distal neuronal
cells…’ or ‘through activating the striate cortex…’ indicate underlying
intermediating neurobiological processes responsible for this direct
experience, expressible in a neuroscientific language with a very different
semantic import. The argument of science is based on a confusion between
ordinary and scientific languages.
5.
Phenomenalist objection
There is still a phenomenalist objection. The
objection can be expressed as follows: The internal contents, the sense data,
are of a mental, psychological nature. If through the satisfaction of a
criterion of external reality, they are interpreted or projected as external,
turning into external contents – for instance, this computer with its singularized
properties like weight, hardness, colors, luminosity, forms… – then these contents must remain mental or
psychological. This means that the external world is phenomenally constituted
by internal, psychological constituents, which are externalized sense data!
This means idealism, if not also solipsism.
Against this radical view there is a Kantian middle
way solution: what we usually call the external world is constituted by mental
phenomena, but there is something beyond them that is the world as a
thing-in-itself (Ding an sich), an x that is beyond cognition. This thing-in-itself
is noumenal, that is, it must be
beyond the phenomenal domain, which also means beyond the reach of our
knowledge. In this way, grounding what we know by means of what we do not know,
Kant arrives at his transcendental idealism. This would be the most reasonable
way to solve the problem.
The answer I can give is that, although this
seems to be the most reasonable solution, it creates another equally serious difficulty.
How to justify the existence of this thing-in-itself? Is it not an odd, empty
hypothesis that cannot be proven and is consequently senseless? One answer to
the problem is that the thing-in-itself should not be thought of as a real
thing. It must be thought of as something dim, like the reverse side of a sheet
of paper, when the first side is the phenomenal side. But then, how can we know
that our phenomenal world is like a sheet of paper wich has another side and we
do not even know what kind of thing the other side is? The metaphor thus does
not seems very helpful.
I believe
that we do not need to fall into the traps of transcendental idealism in order
to solve the problem. When the content of sensation, the sense data, the
qualia, satisfies the criterion of reality, that is, the conditions of
externality and reality, it can be interpreted-projected-relocated as something
qualitatively identical in the external world. This content, when considered as
satisfying the criterion of reality, is simply defined as an external spatiotemporal singularized property (trope)
or a bunch of external compresent singularized properties, namely, as a
material object, or as any combination of these two things building external
empirical facts (states of affairs, events, processes…).[3]
My proposal is that with this kind of direct realism we not only have the cake but also permission to eat it. But isn’t this just a hat trick? My answer is that if it is magic, it is the sort we find in everyday life, like those of sun rising and flowers blooming. In the same way we need to get used to time dilation in physics, we need to get used to thinking that internal psychological content, if it satisfies the criterion of external reality, allows us to project or situate or relocate it into the external world as an external physical content.
Finally, one can guess if there is not an ontologically deeper glue joining these contents, which is that both are made up of singularized properties (tropes): the external content must be made of external singularized properties that are physical ones, while the internal content must be made up of internal singularized properties, which from our perspective are mental or psychological ones, though constituted by physical tropes. Because both contents are structures made up of properties singularized in space and time, they can be seen as qualitatively identical, in this way justifying our cognitive access to the external world.
Literature
Ayer, A. J. (1973). The Central Questions of Philosophy. London: Weidenfeld &
Nicolson.
Costa, Claudio (2018). Philosophical Semantics: Reintegrating Theoretical Philosophy (Newcastle
upon Tyne: Cambridge Scholars Publishing).
- (2014) Lines
of Thought: Rethinking Philosophical Assumptions (Newcastle upon Tyne:
Cambridge Scholars Publishing).
Gallant, J., A., G. Huth, Tyler Lee, Shinji Nishimoto,
N. I. Bilenko, A. T. Vu, (2016)
“Decoding the Semantic Content of Natural Movies from Human Brain
Activity”. Frontiers in System
Neuroscience.
Searle, J. R. (2015). Seeing Things as they Are. Oxford: Oxford University Press.
Teeple R. C., Caplan J. P., Stem T. A. (2009). ‘Visual
Hallucinations: Differential Diagnosis and Treatment.’ Primary Care Companion to the Journal of Clinical Psychiatry, 11
(1), 2009, 26-32.
Williams, D. C. (2018) The Elements and Patterns of Being. Oxford: Oxford University
Press.
Wittgenstein, Ludwig (1965). The Blue and the Brown Books. Harper Perennial.
Nenhum comentário:
Postar um comentário