An illusion is perception not accurately representing external reality. So the perception by itself cannot be an illusion, since an illusion is a relation (mismatch) between perception and reality. The Müller-Lyer illusion is a mismatch between the perception “line A looks longer than line B” (which is true) and the state of affairs “line A is longer than line B” (which is false). The physical line on the paper is not longer, but it looks longer. The reason is that sense information is already preprocessed before it arrives in the part of the brain which creates a conscious perception. We don’t perceive the raw pixels, so to speak, but something that is enhanced in various ways, which leads to various optical illusions in edge scenarios.
I think I agree: perceptions are fallible representations of reality, but infallible representations of themselves. If I think I see a cat, I may be wrong about reality (it’s actually a raccoon) but I’m not wrong about having had the perception of a cat.
An illusion is perception not accurately representing external reality. So the perception by itself cannot be an illusion, since an illusion is a relation (mismatch) between perception and reality. The Müller-Lyer illusion is a mismatch between the perception “line A looks longer than line B” (which is true) and the state of affairs “line A is longer than line B” (which is false). The physical line on the paper is not longer, but it looks longer. The reason is that sense information is already preprocessed before it arrives in the part of the brain which creates a conscious perception. We don’t perceive the raw pixels, so to speak, but something that is enhanced in various ways, which leads to various optical illusions in edge scenarios.
I think I agree: perceptions are fallible representations of reality, but infallible representations of themselves. If I think I see a cat, I may be wrong about reality (it’s actually a raccoon) but I’m not wrong about having had the perception of a cat.