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1
Introduction
When I was very young, I shared a room with my much older brother. I was afraid of the dark. I would fall asleep with the side lamp on. Sometimes, I would wake up later, in the dark. My brother Gerard would have gone to bed in the meantime and switched out the light. I felt quite safe for most of the time we shared the room.
But one night, I woke up and the light was still on. My brother was reading. I sat back abruptly and struck my head (or something like that). A moment later, I was looking up at the ceiling. It appeared as if purple spots swarmed there.
“Gerard,” I said, in a low voice.
“What?” he said, bored.
“There’s something moving on the ceiling.”
He paused for a moment. Then he closed his book and leaned over.
“They’re gremlins, Sean,” he whispered. “Don’t move or they’ll get you.”
He switched off the light.
1.1 Trustworthy Experience
Can we trust our experiences? Can we hold them as a source of knowledge about the world? Can experiences (or appearances or instances of phenomenology) ground our beliefs so that beliefs based on them are instances of knowledge?
Based on some events in my childhood, I want to deny that experiences can always be trustworthy.1 I do not want it to be that there were strange creatures on the ceiling, even if it appears that way to me. At the very least, I want to deny some descriptions and explanations of that experience, such as those given by my brother.
Furthermore, in a broadest set of possible worlds, there are reasons for holding that we cannot trust experience. It is possible that a subject is having deceitful or erroneous experiences. For example, the subject could be dreaming or fooled by an evil genius, a brain in a vat, or a battery in the Matrix. In all these cases, how things appear—particular objects and events in the actual world around the subject—is not how things are. The appearance of actual, particular objects and events occurs in the absence of those actual, particular objects and events.
In response to this problem from erroneous experiences, some epistemologists advance externalist theories of knowledge. If the processes that give rise to a belief are reliable, then even if the believer has no awareness of what makes that belief reliable, that belief can be knowledge. So even if we do not know if the processes giving rise to our experiences are reliable or not, so long as we are in fact having reliable experiences, then any belief based on them is knowledge (for discussion, e.g., Pritchard 2016).
Similarly, in perceptual theory, perceptual theorists, disjunctivists, defend a view that there are ‘bad’ and ‘good’ perceptions. The good perceptions are veridical, the bad not. They otherwise have nothing in common, despite their appearing to have something in common—e.g., hallucinations are bad perceptions (or, even, not really perceptions at all)—yet appear to the subject as the same as veridical perceptions (for discussion, see Logue 2015).
However, these approaches raise a problem for the subject of the perception. They ignore reasons or justificatory factors which are internal—i.e., capable of being accessed by reflection or introspection. Under an externalist or disjunctivist analysis of experience, the subject cannot tell apart cases of knowledge and false belief or cases of good perception and bad perception.
This problem is particularly troubling in cases involving experience. An experience of x is an appearance of x. The appearance of something seems to be something that is accessible to us. In the epistemological sense, the appearance of something is internal; it is accessible to the subject; in their reasoning about the world, the subject can employ appearances.
Experience may be reliable in these cases and so a justified source of belief and knowledge. However, experience is reliable (and distinguishable from unreliable experiences) because of something inaccessible through subjects’ experiences. It is not because of how things appear to us through our experiences. Instead, it is something else that does this work. As the subjects of perception, we may have a ‘good’ experience of the world but we cannot tell it apart from the ‘bad’ experience.
If we identify such an experience’s trustworthiness with its reliability, this leaves an important problem untouched. For any particular experience, the question ‘can I trust this experience?’ goes unanswered. Only others can tell me if I can trust it—and even then, only if their knowledge of the world is itself trustworthy—i.e., if their own experience is a source of justification which is accessible to them (which it may not be).
These thoughts may promote the view that in working out what is true of the world, we should do so without trusting experience. We might say we should not be empiricists (or at least not naïve empiricists). We should be rationalists or, at least, develop a form of empiricism that does not have experience as an epistemological ground (the particular way of distinguishing these positions follows Musgrave 1993). Whatever such alternatives are like, in these models, knowledge of the world (including its grounds and method of acquisition) is independent of our experience. We might call experience epistemologically epiphenomenal.
Yet can we have knowledge of the world without some of it depending on experience? We may well have knowledge of what is necessary and even of what is possible. However, even with such knowledge, a problem remains. With experience, we may know what is true of any world, or what is necessarily true. However, without experience, it is not clear how we can know what is true of contingencies in the actual world.
1.2 Knowledge of the Actual World
One worry that motivates this book is that, without experience, we cannot know about an important class of actual things (including events and objects). These are contingent things: things in the actual world that are not necessary things. They need not be true in every possible world (e.g., there is a possible world in which stars and atoms do not exist). It seems that to know which of a range of possible worlds we are in, to pick out the actual things over the possible and necessary things, we need to rely in some way on experience. If we cannot rely on experience, then I am not sure how we can know about what is actual.
Knowledge without experience can be coherent; it can be general or particular; it can be knowledge of many possible worlds. I can know true things about possible creatures such as gryphons and chimeras, such as the differences between them, without ever having experienced a gryphon or chimera. However, although such knowledge is possible, it can still fail to apply to the actual world. Whatever it is I know about gryphons or chimeras, without gaining this knowledge through experience, I cannot know if any such creatures actually exist.
I think that this role for experience is one reason to prefer empiricism, even a naïve form of empiricism, to rationalism. Something like this worry is found in the thinking at least one early empiricist. Discussing the medieval theory of demonology (a theory of witches, magic, and demons), Montaigne was dismissive of it. However, it is not obvious that he dismissed it because it was irrational. According to the historian Clarke, demonology’s claims are logically possible. The beliefs one holds in accepting demonology are coherent with each other. However, Montaigne objected to it because its rationality is insufficient justification for holding that the entities particular to demonology belong to the actual world. The problem with a theory based on reason alone is that
what reason does “is ask how such a thing happens; what it should do is question whether it happens at all.” “Reason invents an ‘other’ world that is rationally coherent, complete with reasons and causes, but without foundation or substance.”
[…] The result is that “we know the foundations of and causes of a thousand things that never were.”
(Clark 2007, 289; also, Montaigne n.d.)
Despite being a rational theory, a theory may not correspond to the actual world. More precisely, it may correspond to some things in the actual world, the things that are necessary—e.g., the identity of the smallest prime number—that is, what must be true in any possible world. Yet other unnecessary but possible aspects of the theory may not correspond to things that are contingent—i.e., what is particular to the actual world. If that is so, then, even given a rational theory, the following question remains. How do we know about contingent things in the actual world?
A naïve answer is that we either know about the contingent things in the actual world through their being perceptually apparent to us or by their being inferred from what is perceptually apparent to us.2 That is, we know about the actual world based on perceptual experience (or, also, as I call it sometimes, perceptual appearances or the phenomenology of perception).
Perceptual experience is not merely perception. They can be independent of each other. Perceptual experience is what a phenomenologically rich perception is like. It is also what a convincing hallucination or illusion is like. It is what disjunctivists deny is shared by perception, on the one hand, and hallucinations or illusions, on the other. Perception has success conditions; we only perceive if we successfully do so. One can have unconscious perception without experience (e.g., Humphrey 2008)—e.g., you perceive when you flinch away from something, but you do not experience it.
The suggestion here is that perceptual experience matters by giving a particular access to the contingencies of the actual world. As such, to know these things, I have reason to want perceptual experience to be trustworthy.
Even if they are not explicit about it, philosophers of perception accept that perception and perceptual experience play this justificatory role. For example, in his introduction to an edited anthology dedicated to the philosophy of perception, Matthen refers to experience through perception (which I assume is perceptual experience):
Perception is the ultimate source of knowledge about contingent facts. We know about our surroundings because we are able to experience them through perception; we know about scientific phenomena because they are observed. Epistemology is therefore very much concerned with the evidential value of perception. Analytic epistemology is concerned with the rational grounding that perception lends belief; empiricist philosophy of science erects the entire edifice of scientific knowledge on the back of perceptual observation.
(Matthen 2015, 1)
Siegel and Silins write,
Seeing a jar of mustard in the refrigerator can give you reason to believe that the fridge contains mustard. […] When you see a jar of mustard, you have a perceptual experience […] [W]hen experiences provide reason for beliefs, they justify them. […] In this entry, we begin from the assumption that [perceptual] experiences […] can justify external world beliefs about the things you see.
(Siegel & Silins 2015, 781)
That is, for claims about the merely actual world and about contingent facts, reason alone is not sufficient to test or justify such claims. However, perceptual experience can do that. It can play that role of testing or justifying such claims. If that is correct, we can take perceptual experience as a way of testing one’s theories about the actual world.
This does not mean that experience must be of everything contingent about the actual world. However, if taken seriously, experience picks out some of the contingent things, and we can say we know about these things. As for contingent things about which we have beliefs wholly independent of our experience, I am not sure what we can say about them. For example, say I believe that there are gryphons living in my neighbour-hood, yet this belief has no grounding in any of my perceptual experiences. Gryphons are creatures resembling a lion with the head of bird; they seem to be something that I could perceptually experience. In the absence of such experience, then, even if it is true that there are gryphons, I do not know what else could make my belief justified.
This is a very simple picture of how one might use perceptual experience to test theories about the actual world. It involves a naïve theory of perception—a theory focused only on the actual world. It may not work for all possible kinds of experience (e.g., those possible experiences had by demon-fooled spirits or brains in vats), but at least we can trust it for actual kinds of experience.
Unfortunately, there are significant challenges to this naïvety about perceptual experience.
1.3 Erroneous Perceptual Experiences
The most important challenge to naïvety about perceptual experience is that there appears to be overwhelming evidence that subjects of perceptual experience are subjects of actual cases of what I shall call erroneous perceptual experiences. These erroneous perceptual experiences are not only possible cases of erroneous experience, as they might be in classic epistemological thought experiments (such as being a brain in a vat or a mind misled by an evil genius). These are cases of actual erroneous perceptual experience, with actual evidence in support of them.
There seems to be overwhelming evidence for actual erroneous experiences. Many of these experiences are common and easy to generate. There are many websites and picture books with perceptual illusions. (It is even easy for many people to draw some of them, given a good straight edge.)
If it is so easy to acquire such evidence of erroneous perceptual experience, then there is evidence that a perceptual experience of something is easy to generate in the absence of the actual thing. This provides good reasons to doubt that how things appear is trustworthy evidence of how things are. Furthermore, even if such erroneous perceptual experiences were uncommon (as hallucinations tend to be), a single instance of such erroneous experience is enough to show that appearances can separate from reality.
As such, there is reason to doubt that appearances are trustworthy, exceptionless grounds for claims about the actual world. For, if anything can seem to happen without actually happening, what reason do we have to treat that something seems to happen is a reason to believe that it is happening?
One reason to treat appearances as corresponding to reality is that one wants how things seem in perception to justify beliefs about how things are. Again, one wants to use experience to pick out what is true of the actual world.
However, desire is not enough to make it a perceptual experience trustworthy. What we need is a reason to trust experience, not just a desire to trust experience.
Although this desire is not a reason to trust experience, it can be a reason to prefer one theory to another. One can prefer the theory tha...
