Tag Archives: epistemology

What does an illusion of x show?

Previous post: what perceptual theories should explain about illusions.

Previous post: universal illusory counterparts

I assume that I am not under a universal illusion. Of course, I would assume that even were I under a universal illusion.

Just as I cannot assume that how things seem is how things are, so I cannot assume that how things seem is not how things are. I agree with Levin 2000 that, although it is possible that I am under a universal illusion, it is also possible that I am not under a universal illusion; further, it is difficult to find evidence that would decide for the former.

If I assume that, then the possibility that I am under such a universal illusion is not something I will try to prove or disprove. What then is the point of discussing universal illusion? To illustrate the following: there can be illusions; a subject of an illusion can fail to detect that they are under an illusion; just because something is apparent does not mean that it is how things are. Thus, if one is naive, and takes all appearances to be how they are (colour? Shape?), one could be misled without knowing it(about colour? Shape?).[1]

And so one might think this: although there may not be evidence of a universal illusion, surely there is evidence that we are capable of being under such a universal illusion. That is, there is no evidence that, for everything I seem to have experienced, all of the object and properties that are or have been apparent to me, are illusory; but there is evidence that I am capable of such illusory experiences, regarding any objects and properties that are or have been apparent to me. That is, based on how I am constituted in this world, I am capable of being misled regarding anything that is apparent to me.

But are we sure there is evidence for such a capacity for universal illusion?

What sort of evidence is there? Well, how about: people hallucinate — even do so easily, given the circumstances, such as a sensory deprivation tank; people experience distortions in sound, smell, sight, and touch; people dream so vividly that they believe, on waking, that it was no dream. People have false memories (and of course false expectations, but this would be a different meaning for ‘illusion’); people have after-images, which they do not know as being ‘in the mind’ (or whatever is going on there) and interpret as being out in the world. By my own analysis (Power 2011, and discussed in the footnotes of this post), Perky’s results suggest people can even have illusions in their imagination.

This plenitude of distortion and misleading appearances suggests that these are only a sample of what goes wrong, for any mode of perception, and that the list of illusions which our perceptual system is capable of extends much further. So, from this, we might conclude that,  our perceptual system is capable of any illusion. For any veridical appearance, there can be a non-veridical, illusory counterpart appearance, i.e., we can assume a principle of universal illusory counterparts.

What can be drawn from an illusion of x

We might conclude this, but it is worth being slow about it. To do so would be equivalent to concluding that, because there are so many ways you can pull apart an object, then one can actually pull it apart in any conceivable way. This would be a controversial assumption, and it ought to be for perception as well. We might conceive of an appearance of P without P being real, but this does not mean that, for any actual subject, there can be an appearance of that P without P being real. It would only follow if one assumed a principle of universal illusion; but the point here is not to assume the principle of universal illusion, but to provide evidence in support of universal illusion.[2]

Instead I think you should only draw the following (here, I mean by ‘y depends on x’, in cases of properties, that for there to be an instance of y, there must be an instance of x):

1. Trivially: each example of illusion, each illusion of an x is evidence that there can be an illusion of that x. That certainly has consequences just from that particular discrepancy between appearance and reality. For that x, its appearance does not mean that we conclude that there is an x. But this does not mean that an illusion of x shows we are capable of an illusion of anything other than x. Unless:

2. Since the appearance of x can occur without actual x, then if the appearance of something else, call it y, depends on the appearance of x, it can occur without there being an x.

To use an example from my 2011, a house can look like a giant castle if its appearance as a giant castle depends, on the one hand, on its apparent shape and, on the other hand, on its apparent distance. If its apparent distance is illusory, it’s ‘giant castle-ness’ will be illusory. One can easily demonstrate dependencies about distance, shape and size, e.g., as seen in Bernard Pras’ work: http://www.bernardpras.fr/

Such illusions, however, do not show illusions which do not depend in this way on x, i.e., some z that is not y. The shape or size of something can be distorted by distortions in distance, but this does not mean that its colour or shade can; one must show something else for that. Nor do they show that these dependent illusions, the ‘y’s, are illusions of the other apparent properties; distance may show the size is distorted, but fail to show the shape is distorted.

Of course, other illusions might do this (and I can think of some that do for the particular examples) but that does not mean that the offered example of illusion shows it. And this should not be surprising. Consider the examples of illusions above, of the Ebbinghaus illusion and the ‘checker shadow’ illusion. From the Ebbinghaus illusion, one can safely infer that the relative size between objects (x) can be illusory. But it is not obvious that one may conclude from the Ebbinghaus illusion what is shown in the ‘checked shadow’ illusion, that a difference in shade can be illusory (y). Further, even if one did think this, it would be because they can show that the differences in shade (y) is in some way dependent on what is illusory in the Ebbinghaus, the differences in size (x), i.e., just the point made here.

3. The opposite dependency relation that is in ‘2’ is this: Unless the appearance of x itself depends on z, then the dependency of x on z does not guarantee that, from the appearance of x, there is a z.

Say that the shape, x, of an object O depends on z, a particular set of three-dimensional properties in physical space, e.g., an object’s apple-shape depends on the object’s ‘fairly-spherical’ three-dimensional properties (this is very rough, I know). If O merely appears to be x, that there is an illusion of x in perceiving O, then from the mere appearance of x, O’s apparent apple-shape, one cannot conclude that there is a z, that O has fairly-spherical three-dimensional properties.

Of course, it might still have those three-dimensional properties. But you can’t take that from its apparent apple-shape, because it really isn’t apple-shaped. If it was really apple-shaped, then you could conclude that it had those three dimensional-properties. But then there would be no illusion here of the apple shape, the x in this example.

From ‘1’, ‘2’, and ‘3’, one can draw other conclusions: mutually dependent properties are combinations of ‘2’ and ‘3’. The point is, other than these three conclusion, I am not sure what else one can draw from an illusion of x. (Suggestions are welcome).

Illusions of space and time

Someone might wonder: so what?  This is all very well if one did not know the following:

There can be illusions of fundamental properties, properties on which most other properties depend. These are properties of space and time — that is, there can be illusions of space and illusions of time.

Thus, there can be illusions of any properties dependent on their occurrence on spatial and temporal properties (or their appearance on the appearance of spatial and temporal properties).   Most properties, especially in the phenomenology of perception, depend on spatial and temporal properties.

And there are lots of instances of illusory spatial and temporal properties.


It’s Now Over There: illusions of space (there) and time (now)(in development)

Illusion and the embedded and extended mind debate

1. Some philosophers (e.g., Crane 2006, Tye 2007, and Harman(discussed in Lycan 1996)) claim that, in having an experience, what is apparent to us, e.g., what we seem to see, hear, touch, etc., seems not to belong to the experience itself, but only to belong to things in the external world, independent of experience itself. The experience’s own properties are not apparent to us at all. Tye refers to this as the ‘transparency’ of experience; Crane refers to it as the ‘diaphanousness’ of experience.

One point I think could be drawn from the issue with illusion is that, even if it seems that way, that experience is transparent, that we only experience properties of external things, we possibility of universal illusion means that cannot be sure that it is that way. But, again, it does not mean that we cannot be sure that it is not that way either. My point throughout is that, without actual evidence for one or the other, I think one has to either throw up one’s hands and then sit on them about the whole affair, or draw on the only thing available to prefer one or ther other: appearances themselves, that it seems that way.

[A footnote to the footnote: on the claim that transparency/diaphanousness -> we do not experience the properties of experience themselves.

Because I am interested in the structure of experience, in how it is constituted and its spatiotemporal conditions, and, further, I am sympathetic to positions involving an object being necessary and presented for experience (somewhat in the spirit of naive realism and indirect realism) I tend to take it that, in one way at least, it should be an open possibility that we experience properties that  strictly (though indirectly) belong the experience.

These are properties of the object of experience under a conception of the experience/object relation as one where the object is a constituent of the experience. In that case, one might say that we experience a part or constituent of experience, the part being the object of the experience, or its properties. If we think of the whole inheriting the properties of its parts (e.g., a woolly mammoth is woolly — except, of course, only part of it is woolly(its tusks, eyes, and toes aren’t)), then we are in this sense experiencing properties of the experience.

I think is reasonable to think that is a metaphysical claim about experience; it is not a naive claim, or simply pointing out the phenomenology of experience, i.e., how we describe it. But I also think that the alternative is not a naive claim, a simple pointing out of the phenomenology, either: that, conceiving of experience as something that happens,  then experience is something completely separate to what we experience, what we experience is not part of experience.

After all, the very motivation for transparency/diaphanousness is that the phenomenology, in having an experience, is only of the object and its properties, of what we experience. In ignorance of the complex processes involved in experience, one might think that all there is to experience is what is experienced; all that is happening is only what we are experiencing. In that case, one experiences the properties of experience because the only properties experience has are the properties of what we experience.

Of course, I do not assume that this is true, nor do I expect anyone else to assume it in this debate. But I do not think it is false because experience is separate or separable from what we experience. It is my view that, for various reasons, one might want to develop an account of experience that says experience includes the properties of what we experience, and more, rather than excludes those properties (which are, again, the only ones of which we are aware in having an experience).

(I will say more about this in a later post)]

2. One might think that the fact we are talking about appearances means automatically that there can be an illusion. That is, an: appearance of x -> possibly ( illusion of x).

First, as the discussion so far should show, the issue doesn’t just concern the possibility of illusion. It concerns there being evidence that, given how our actual perception works, that, for a particular x, x can appear without being real.

Second, it is true that ‘appearance’ and ‘not real’ are compatible, that ‘apparent(x) and ~x’ is a coherent phrase, and that an entity can have the concept of ‘appearance’  and ‘unreal’ or ‘not real’ coherently applied to it (in contrast, the special concept I introduce as ‘obviousness‘ is not compatible with ‘not real’; ‘obvious(x) and ~x’ is incoherent — as incidentally is ‘obvious(x)’ and ~apparent(x)’). But that something is conceivable, again, does not mean we have to satisfy it with our explanations about how actual perception works (something similar is argued by Harman, discussed in Arstilla 2005). 

(I can think of at least one group of theorists should agree with this last point: those who hold that some apparent properties are only apparent, without there being any case where they correspond to something real, e.g., representational physicalists who agree that qualia  (1) are apparent and (2) are non-physical but reject having to accept them as something real (e.g., Dennett 1991, perhaps; Lycan 1996; discussed by Crane 2006).  For reasons that have been touched on so far, I think one should resist approaching the problems of consciousness in this way, but never mind that now).

Universal Illusory Counterparts

Previous: Conditions of Illusion II

Ought we hold the following as a principle about experience?

For any entity or property x that can be apparent, in cases where there is no x, our perceptual (and, more broadly, experiential) capacities include the ability to generate appearances of x.

Here is either the same idea put in a different way or an ever-so-slightly different idea:

Due to how actual experience is constituted, it is possible that, for any appearance of x, x’s appearance can occur without x. How actual experience is constituted includes the capacity, for any apparent x, that there is an illusion of x.

Here is one more way of putting it.

For every case where appearances and reality match, then given our experiential capacities, it is possible for there to be a counterpart case where appearances and reality do not match.

(I think it is plausible that) It follows from holding this (or any of these, if they are different) as a principle that, for every veridical experience, every case where how things appear is how things are, there can be a counterpart non-veridical experience where how things appearis not how things are.[1]

Expressed in the last way, I call this the Principle of Universal Illusory Counterparts.

Dallas Pam

Seeking an answer to the sceptics’ challenge to the dogmatists, Descartes decides to put aside all beliefs about which he had reason to doubt. In Meditation 1, he begins with beliefs derived from the senses:

“All that I have, up to this moment, accepted as possessed of the highest truth and certainty, I received either from or through the senses. I observed, however, that these sometimes misled us; and it is the part of prudence not to place absolute confidence in that by which we have even once been deceived.”

Descartes then moves on to the possibility that everything, no matter how certain it seems, is not how things are. This includes the certainty that one is awake: he allows the possibility that, even as one is certain one is awake, it is the case that one is dreaming.

Let us assume that this is possible: your whole life is, and has been, a dream. Everything that you seem to remember, and everything you seem to see, hear, and otherwise perceive, is not how things are. Or, perhaps, let’s not even go this far. Let’s just go back to your teenage years (if you’re an adult) or childhood (if you’re a teenager): some night, you went to sleep and dreamed everything that appears to have happened to you since then. You are still in that night, dreaming, much younger than it seems to you that you are. At some point in the future, maybe before the end of this sentence, maybe much further in this dreamed life, you will wake up. This life you believe you have lived has no existence. All the people around you are fictions. When you wake up, it will stay with you as any dream does, perhaps make you feel — briefly– sad, amazed, uncertain, relieved, but like all dreams it will fade. Like most dreams I’ve ever had, you’ll forget the details soon enough and simply say ‘I had such a strange dream. I was so much older than I am now, and this happened — and this — and this’, but then you will get on with your — so it seems to you — real waking life.

If the above is possible, then this is also possible: The vivacious, rich, detailed experience in perception (and remembering) is entirely mistaken. It seems to be of a rich, mind-independent world, full of  spatial and temporal entities possessing mind-independent and even body-independent properties such as shape, timbre, colour, weight; but this experience is not of those entities and properties. Even if there are such entities and properties, you have no experience of them. What seems to you to be perceptions or memories are not connected in the ‘right way’ to them (e.g., through causal chains, Coates 2000).

I do not want to dispute this possibility. To put it in terms of possible worlds, I will assume like many that: there is a possible world which seems exactly the same as the actual one but which is completely different to the actual world on the macroscopic and otherwise observable scale.(Although Bouiswama 1949 has an interesting way of resisting this idea.)[2]

However, I do want to dispute that there is a need to accommodate such a world in our explanations of our own perception and experience — that is, of the perceptual and experiential systems that we ourselves, actual beings in this world, possess.

Next Posts


1. This is not to say that, for any particular x, this ever happens to either ourselves or any other actual individual being that has experience. It is only to say that it is possible, given any such actual beings’ capacities. The range of possible ways actual experience can occur, given how it actually works, includes a separation of appearance and reality for any x (which is I suppose another way of putting this).

2. Putnam discusses the relevances of differences on the microscopic scale to psychological states, in terms of their reference/content/meaning, and truth-value. Perhaps one could also run something similar on the cosmological scale, so that if a subject ended up, unknown to themselves, passing through a multiversal wormhole into a universe in which the galaxies are not drifting apart, or where the sun is the centre of the universe, they would mean a different thing when they talk about the sun thinking, or the milky way galaxy glowing beautifully at night. But, in any case, I don’t think that water happening to be H2O or the universe being properly described according to a sort of neo-Ptolemaic system would make our experience of the world mistaken or illusory in the sense intended here.