Monthly Archives: May 2012

First steps: Time and the metaphysical condition of illusion

Previous: Conditions of Illusion I

Note: Most of the ideas here are developed further in my 2018 book, Philosophy of Time and Perceptual Experience.

The metaphysical condition on illusion means that, if there is an illusion, then the world is a certain way. There are certain things that are real in the world, certain others that are not. The appearances in cases of illusion then fail to match this way the world is: either it seems as if (a) things are real which are not real or (b) things are unreal which are real [1]. For the sake of this discussion from now, I’ll normally talk only about cases of (a): where it seems as if things are real which are not real. There are one or two exceptions to this, as will turn up as we go along [2].

So, this seems right:

1. If x is unreal, and it appears as if x is real, i.e., there is a discrepancy between the appearance and reality of x, then there is an illusion of x.

At this stage, we can introduce the broad relevance of the metaphysics of time.

It is this: there are contemporary debates in the metaphysics of time about the reality of things, events and properties in time. Which side you fall on in this debate at least partially determines what you hold to be real (it does not wholly do it, of course; there will be other factors in what you hold to be real, as I’ll come to). Thus, one can say this initially:  That there is a discrepancy between x’s reality, and the appearance of x’s reality, may be partially determined by the reality of x in time. And so:

2. That there is a discrepancy between x’s reality, and the appearance of x’s reality, may be determined by which metaphysical position of time is correct.


1. I prefer to speak this way even though it raises the, to some, thorny issue of referring to things that are unreal. I could translate ‘there are things that are unreal’ to some sentence which does not even seem to refer to ‘things’. This is an issue in philosophy but not one I feel I need resolve. Similarly, I talk about things that seem real but are not real. ‘Things’ could refer to objects or they maybe refer to properties (as will be seen, I even use it to cover events). Philosophers tend to draw a line between illusions and hallucinations based on whether or not it is objects or properties that seem to be the case (or real) but are not the case (or real). This distinction is important, later, but I don’t want to make it here, for now.

2. E.g., the Perky effect, a common interpretation of which is that subjects interpreted what they actually see as merely being visually imagined. In my 2011b, I argue that this is an example of illusion in the experience of sensory imagining, and so not perceptual illusion. I think some will think this is not right, because, e.g., the only experience of which there can be illusions are perceptions of properties belonging to external things; I discuss this in the section on Conditions of Illusion II.

There is another reason one might reject this example as evidence of such illusion. From recent conference and personal discussion, I’ve become aware that the set-up and even basic interpretation of the Perky effect is being called into question (I’m thinking here of discussion in two workshops in Glasgow in 2011, one on cross-modal effects (in March 2011) and one on  ‘Imagination and Memory’ (in September 2011)). I think this is less important: it may be that there is no empirical evidence of this occurring to us, and so no actual cases of mistaken imaginings. Every time we have an experience that seems to be imagining some x, it is imagining x; there are no erroneous cases. Still, my point here is: if there were such cases, because there is a discrepancy between appearance and reality, they would be illusions. (For other very recent philosophical discussions about the Perky Effect, see Hopkins 2012 and Nanay 2012’s reply to Hopkins (in the same issue)).



The Ebbinghaus illusion: two orange circles, one surrounded by large blue circles, the other surrounded by small blue circles

The Ebbinghaus Illusion.

Previous post: Introduction.

Note: Most of the ideas here are developed further in my 2018 book, Philosophy of Time and Perceptual Experience.

As an example of what I’ve been developing about this subject, here is what I think is necessary in order for something to be an illusion. The implications are significant, and will feed into the rest of the work.

Three conditions of illusion

I think this: to get an illusion, at least three conditions must be satisfied:

  1. The phenomenological condition: for there to be an illusion of something (x) there needs to be an appearance of x. E.g., in the Ebbinghaus illusion above, the two orange circles appear to be different sizes.
  2. The metaphysical condition: there needs to be a way things are — a way things actually or really are. ‘Possibly’ isn’t enough; neither is there being a way things are believed, imagined, hoped, etc., to be; that is, it is not enough that for an illusion that things are merely intended to be (in the broadest sense of ‘intended’). E.g., in the illusion, the two orange circles are really the same size (and it is not just that we believe or think that they are the same size).
  3. The discrepancy condition: The appearance of x must fail to correspond to reality; there must be a discrepancy between, how things seems and how things (actually or really) are. That is, how x is described under the phenomenological condition does not correspond to how things are described under the metaphysical condition. E.g., there is a discrepancy between the apparent size of the orange circles and the real size of the orange circles.

Remove one of these conditions, and there is no illusion.

— If x is in no way apparent to you, e.g., if it is hidden, or too small to see, or too light to feel, or too far away and too quiet to hear, then there can be no illusion. You can of course make a misjudgement about it anyhow: believing it is there, and being correct that it is, you might still think it is some way that it is not. Someone tells you that your brother’s car is in the garage; you remember your brother’s car is yellow, and so judge/imagine/expect etc., that there is a yellow car in the garage. But your brother re-painted his car and it is now red; so you make a misjudgement, you imagine wrongly, your humble expectations will not be met. Wrong as you are, you are not here under an illusion.

— ‘2’ is the most difficult one for me, at least, to remove in the definition. This is because I am what some philosophers call a ‘realist’. I hold that there is something the way the world is independent of what I or anyone (at all, anywhere, ever) believes, hopes, intends, represents, etc. of the world. This does not preclude my beliefs etc. corresponding to the way the world is (otherwise I might be a skeptic, or some variant of skeptic at least) ; nor do I know how I came about my beliefs about the world; nor am I clear how I could justify such beliefs. But I do think that the world is a certain way, no matter what I think.

Others might have other views, and deny that there is a way the world is. Or, they might refuse to engage with such an assertion, sticking perhaps to how things seem and one’s beliefs, and leaving it at that. If so, I do not know why they would ever assert cases of illusions. My uncertainty comes of this: given only appearances without any idea of reality, then something appears to be some way; but, one cannot say if it is that way (because the world isn’t one way or another). So, how can this appearance be — or not be — illusory? One cannot set up the next condition because one cannot say that appearances are mere appearances, fail to match how things are. So what is left to make a case for there being an illusion?

— ‘3’ requires a discrepancy. Remove the need for the discrepancy and I cannot see any reason to hold that there is an illusion. Say one  removes it because one refuses to engage with one of the relata of the discrepancy: one refuses to say how things appear or how things are; or perhaps one does not have an opinion on either or how they are related. In that case, I do not think that one can assert that there is an illusion  — or that there is not an illusion, for that matter. All that can be said is how things seem, or instead how things are, but not both. But I think we do talk about both — even, in fact, particularly in scientific practice — and especially in gathering evidence of illusion and ‘meta-cognitive error’ (which I’ll talk about later). That I’m correct or not about this is one discussion I’m interested in having from this research.

Other philosophers add further conditions, to which I’ll turn to soon in a post. But even at this stage, I think that there are interesting implications for saying that there are illusions of time.

Next posts:

1. First steps: time and the metaphysical condition of illusion

2. Conditions of Illusion II