It is generally agreed that perception involves a real object transferring information about itself into the brain of the perceiver, via the sense organs and nerves; and the distinguishing features of this are that the real object is external to the perceiver and public, while the image of it in the brain is internal and private. My question is: illusions are unreal, but they are external and public --- as with the railroad lines meeting in the distance, or the Sun and the Moon being the same size during an eclipse. So are illusions real, or unreal?

Illusions are "real" in one sense and not in another. Unreal: The railroad lines look to me as if they meet in the distance, but they don't. In this case, reality isn't as it appears to me. Real: I am part of reality, and so are my mental states. One of those is that the railroad tracks (falsely) appear to me to meet in the distance. This is a robust illusion that I and many others are really subject to.

If you watch a car drive away from you down a straight road, it appears to get smaller as it gets farther away. We know that it doesn't *really* get smaller, it only *appears* to get smaller. So we distinguish between the real size of the car and the apparent size (at a particular distance). I have two problems with this. First, at what distance do we see the real size; or, at what distance does the apparent size equal the real size? Second, the real car is supposedly outside our heads and the apparent car is supposedly an image of the real car, and inside our heads. But the car we actually see is (a) outside our heads, so real, and (b) changing its size with distance, so an image inside our heads: but how can it be both?

There are tensions here, I agree, though I think they reside in the way that we talk about appearances rather than in the appearance/reality distinction itself--at least as it applies to cars. Size is an intrinsic property of a car if any property is--that is, a car's size, like its shape, depends entirely upon the way it alone is, and not upon what may or may not hold in the world around it. Apparent-size, by contrast, is a non-intrinsic or relational property of a car, and subtly so: a car's apparent-size depends not just upon the car's size, but also upon the relative location of the relevant viewer. Thus, the car's apparent-size (to Fred) can shrink if the car shrinks in size, but also (and using less magic) if Fred and the car move apart so that light from the car subtends a smaller angle in Fred's visual field (as they say). So, one and the same real car can consistently maintain its size and change its apparent-size through changes only in the relative position of the viewer. This is...

If a tree falls in the forest and there is no one to hear it, it does not make a sound. This makes sense because sound is a perception. Without a perceiver, the falling tree just creates sound waves that are never perceived as sound. But, Schrödinger's cat applies to a living thing whose existence is not dependent on any outside observation. Why is it that the the cat cannot be said to be alive or dead until an observation is made? Seems that the status of the cat is simply unknown until an obervation is made. Please explain.

When the proverbial tree falls in the forest, it vibrates creating sound waves that will, under normal conditions, cause a sound-experience as of a crashing tree in the mind of any normal hearer who is within range. There are plenty of vibrations and sound waves, and conditionas are ideal, but alas, there is no one around in that isolated forest, not even a wood-pixie, to have any sound-experiences at all. Was there a sound nevertheless? I say yes. "Sound" in its primary, objective use picks out, roughly, whatever features underlie the objective auditory properties we take ourself to perceive in the world outside us--vibration-events in the tree, more or less, or perhaps the soundwaves they cause. When I say that I hear the resplendent sound of that trumpet, I take myself to be representing a feature of the trumpet (or it's current activity) not a feature of my mind, though I recognize that my auditory capacities are required to accomplish this representation. Cases of auditory illusion (or...