# A memory is a physical thing. **URL:** \ **Category:** Great Debates\ **Created:** [March 2, 2005, 11:33am UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584 "2005-03-02T11:33:21Z")\ **Posts on this page:** 20\ **Page:** 18
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [March 8, 2005, 11:55am UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/341 "2005-03-08T11:55:04Z")
> [@Lib](#): > > Photons are coming from all over it. And are thus _not the wall_ any more, agreed? > [@](#): > > It is the wall that is physical; the image is just a perception. Are you contending that photons are _nonphysical_? > [@](#): > > The physicalist will declare that perception is physical too. But that’s only because he has taken as axiomatic that anything you name is physical. Again, I have to repeat that this verges on misrepresenting me. I am not _axiomatically claiming_ that thoughts are physical, any more than any other scientist axiomatically claims their proposed explanation for a given phenomenon. I **seek to explore** cognition and entities some people call “metaphysical” using entities we _do_ agree are physical (even if you are only agreeing that there are such here for the sake of argument). If I propose an entity which you _don’t_ consider physical, such as a photon, you can say “Whoa!”, and we can examine it. > [@](#): > > (Paraphrased) **If** the metaphysical exists, is it physical? No it isn’t. I don’t think the metaphysical _does_ exist, but if it did, I’d be wrong. Problem? > [@](#): > > I know what it’s like to change a worldview. I was a materialist. But upon discovery that I was standing in quicksand, I simply stepped out — despite years of emotional baggage and attachment to the theory. He is a man who will not hesitate to do the same. You just watch. I already have - I was a theist, remember, and my ‘divine’ experience was seemingly similar. My change to my current worldview was every bit as difficult as yours. You consider physicalism to be logically difficult to hold, I consider belief in heaven to be utter wishful thinking. We each believe we are wielding Ockham’s Razor correctly. I would ask you only to _listen_ to me here. ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [March 8, 2005, 12:07pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/342 "2005-03-08T12:07:16Z")
> [@SentientMeat](#): > > And are thus _not the wall_ any more, agreed? Nope. Suppose the wall is 10 units by 10 units and the image is on a portion of the wall 5 units by 5 units. Are you going to claim that the 5 unit by 5 unit portion is no longer part of the wall? If you believe that, then remove the wall. If you remove the wall, the image is gone. If you remove the image, the wall is still there. > [@](#): > > Are you contending that photons are _nonphysical_? No. I’m contending that the photons are coming from electron clouds _in the wall_. > [@](#): > > Again, I have to repeat that this verges on misrepresenting me. I am not _axiomatically claiming_ that thoughts are physical, any more than any other scientist axiomatically claims their proposed explanation for a given phenomenon. I **seek to explore** cognition and entities some people call “metaphysical” using entities we _do_ agree are physical (even if you are only agreeing that there are such here for the sake of argument). If I propose an entity which you _don’t_ consider physical, such as a photon, you can say “Whoa!”, and we can examine it. I’ve said whoa, but not because a photon isn’t physical. I’ve said whoa because an image isn’t physical. In fact, unless you find some logical flaw, I’ve proved it. > [@](#): > > No it isn’t. I don’t think the metaphysical _does_ exist, but if it did, I’d be wrong. Problem? Problem is that you aren’t admitting to being wrong. An image isn’t physical. > [@](#): > > I already have - I was a theist, remember, and my ‘divine’ experience was seemingly similar. My change to my current worldview was every bit as difficult as yours. You consider physicalism to be logically difficult to hold, I consider belief in heaven to be utter wishful thinking. We each believe we are wielding Ockham’s Razor correctly. I would ask you only to _listen_ to me here. Tell you what. I’ve got a lot of work to do that could possibly occupy me for days. I’ll wait until you’ve said all that you want to say, and then I’ll read all of it. If you offer a compelling argument, I promise you that I’ll change my mind. That is in fact what I will want to do. Truth is like light — it displaces the darkness. I want light, irrespective of where it leads me. ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [March 8, 2005, 12:17pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/343 "2005-03-08T12:17:20Z")
> [@](#): > > If you remove the wall, the image is gone. Ah, but the _photons_ are still crossing that 2-D plane where it stood, yes? > [@](#): > > No. I’m contending that the photons are coming from electron clouds in the wall. Being _re-emitted_ having interacted with those photons travelling in the opposite direction, which would have continued had the wall not been there, yes? > [@](#): > > I’ve said whoa, but not because a photon isn’t physical. I’ve said whoa because an image isn’t physical. In fact, unless you find some logical flaw, I’ve proved it. Your logical flaw is that photons are not non-physical. > [@](#): > > Problem is that you aren’t admitting to being wrong. An image isn’t physical. Photons are, yes? > [@](#): > > Tell you what. I’ve got a lot of work to do that could possibly occupy me for days. I’ll wait until you’ve said all that you want to say, and then I’ll read all of it. If you offer a compelling argument, I promise you that I’ll change my mind. That is in fact what I will want to do. Truth is like light —— it displaces the darkness. I want light, irrespective of where it leads me. Well, OK. I’ll start like this: _Light is physical_. A camera can capture light. What is a camera? A lens … ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [March 8, 2005, 12:44pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/344 "2005-03-08T12:44:01Z")
And to tie in with my earlier post, **a** reflection isn’t strictly a physical **object** , I suppose. _Reflection_, however, is very definitely a physical **process**. ---
**Author:** ![Arwin](https://avatars.discourse-cdn.com/v4/letter/a/51bf81/32.png) [@Arwin](https://boards.straightdope.com/u/Arwin)\ **Post date:** [March 8, 2005, 1:16pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/345 "2005-03-08T13:16:32Z")
> [@Liberal](#): > > But the massless photons eminate _from the wall_. There has to be an electron whose orbit collapses. And the electron has to be a part of an atom (in the physics sense). The image is merely _a part of the wall_ that is emitting photons that correspond to points in the image. The _whole wall_ is emitting photons. > > All that is to say that the image is merely a perception of the wall. > > If you put a blind man in front of the wall, he will perceive no image. He might perceive a bit of heat as the light heats the wall, but that’s it. You could give him the same effect by using a torch on the opposite side. It is the wall that is physical; the image is just a perception. The blind man would not see the wall either. Just grabbing a random definition of this kind of image from a web-dictionary: > [@](#): > > a visual representation (of an object or scene or person or abstraction) produced on a surface; “they showed us the pictures of their wedding”; “a movie is a series of images projected so rapidly that the eye integrates them” We observe physical objects visually by their reflections striking our eyes. In that sense, we really see the wall in pretty much the same way as we see an image projected onto that wall. In the case of seeing the wall by itself, we see the wall by virtue of the light that is already present and is bounced back to us in a particular way by the wall. In the case of an image projected onto the wall, we see the light of, say, a table, projected onto the wall, and reflected back towards us. Our seeing is the physical reception of light. Every reflection of light is from physical objects. If I were to object to calling everything physical, I would rather say that every object or entity we choose to distinguish from that light-fest, whether it is the wall, or the image, or the combination, or the table in the image, or the table in front of the wall, or the projector, is a mental construct, abstraction, or whatever. If we consider everything that goes on in the mind as physical too, then it is. If we don’t, it isn’t. At this point, we’re getting to the point where you should rather to determine which approach is more useful than which approach is more real. Or rather, realise that thanks to the skeptics, nothing shapes reality other than our own subjective value assignment, objectified only by having more people agree with you on that value assignment. ---
**Author:** ![Hoodoo\_Ulove](https://avatars.discourse-cdn.com/v4/letter/h/58956e/32.png) [@Hoodoo\_Ulove](https://boards.straightdope.com/u/Hoodoo_Ulove)\ **Post date:** [March 8, 2005, 3:38pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/346 "2005-03-08T15:38:59Z")
**Liberal** , did\*\* SM\*\* or any other physicalist assert that Darth Vader’s watering can is physical? Or that it exists? Not the photons on the screen describing it, not any of our memories of discussing it, but the watering can itself? ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [March 8, 2005, 4:02pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/347 "2005-03-08T16:02:26Z")
Actually, **Hoodoo** , I proposed (not quite “asserted”) that it is _as physical as_ the image on my monitor when I have merged two digital photographs in Photoshop. That’s why I’m interested in placing digital photography (_ie._ the photos themselves and the process by which they arise) on a solely physical basis. ---
**Author:** ![Hoodoo\_Ulove](https://avatars.discourse-cdn.com/v4/letter/h/58956e/32.png) [@Hoodoo\_Ulove](https://boards.straightdope.com/u/Hoodoo_Ulove)\ **Post date:** [March 8, 2005, 4:28pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/348 "2005-03-08T16:28:25Z")
**SM** , saying that an imaginary object is as physical as an image on a CRT goes against my common sense. I’m not talking about your idea of the can, or the words of a sentence describing the can, but the fucking can itself, dammit. To place digital photography on a physical basis does not require holding such an absurdity to be true. ---
**Author:** ![other-wise](https://avatars.discourse-cdn.com/v4/letter/o/4bbf92/32.png) [@other-wise](https://boards.straightdope.com/u/other-wise)\ **Post date:** [March 8, 2005, 5:01pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/349 "2005-03-08T17:01:33Z")
> [@SentientMeat](#): > > You are now, instead, asking questions akin to _What are the physical properties of “object”?_ I can only interpret this as you forgoing the baby steps we’re making and bounding way off down the path again to explore the physical nature of our _thoughts_ when we use words like “object”. This is not **yet** what I’m talking about. _Eventually_ I will, by appealing to a kind of ‘average’ of all the memories of things we call “objects”, but let us put this aside for a moment. I don’t think I’m jumping ahead in the sense that I believe my “Something About Mary” argument shows that memory is inextricably linked to awareness, and that awareness has no physical purpose whatsoever. Therefore, even if our thoughts are “_a kind of ‘average’ of all the memories of things we call “objects”_”, the point is moot; memory has an aspect that is not physical. I’ve been trying to re-work the “Something About Mary” argument into a version using computers instead of people in the hopes that you might find the analogy more comfortable and easier to grasp (And please understand, **Sentient** , I’m not “dumbing it down” for you; if anything, I’m dumbing it down for _me_. Because my ability to comprehend far outruns my ability to _articulate_ that comprehension, (plus my formal training is nil), I feel like I’m dog-paddling in the deep end of a pool filled with speedboats). I’m in a Big Crush at work, and can only hit the SDMB when there’s a lull in the action. I’ll post again as soon as I can. > [@](#): > > Now, the tree **falling** _doesn’t need anyone around either_. **Agreed**? Not quite yet. > [@](#): > > Do we agree that the tree falling, _when nobody is around_, is as physical as the tree itself? Again, I hold out my hands ready to catch you if you trip making this step. I appreciate the support, but do I agree? Not quite yet. ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [March 8, 2005, 5:53pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/350 "2005-03-08T17:53:01Z")
> [@Hoodoo](#): > > SM, saying that an imaginary object is as physical as an image on a CRT goes against my common sense. I’m not talking about your idea of the can, or the words of a sentence describing the can, but the fucking can itself, dammit. To place digital photography on a physical basis does not require holding such an absurdity to be true. Ok, OK! The fucking can itself was not “imaginary” when the image/memory was formed. Later, it might have been destroyed while the image/memory remains. Make of that what you will. > [@other-wise](#): > > memory has an aspect that is not physical. And I’m saying that memories which one isn’t _aware_ of is an **access** problem, which is no less physical a problem than dropping your Flash memory in a lake. If it helps, **o-w** , take a look at my recent correspondence with **Lib** here, regarding physical processes and [x, y, z, t] co-ordinates and such. ---
**Author:** ![Hoodoo\_Ulove](https://avatars.discourse-cdn.com/v4/letter/h/58956e/32.png) [@Hoodoo\_Ulove](https://boards.straightdope.com/u/Hoodoo_Ulove)\ **Post date:** [March 8, 2005, 6:27pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/351 "2005-03-08T18:27:28Z")
> [@SentientMeat](#): > > Ok, OK! The fucking can itself was not “imaginary” when the image/memory was formed. Was so! The image wasn’t imaginary but the can was, is and will be until Darth Vader is not fictional. To say otherwise is to fall into Liberal’s game. You’ll be agreeing with the ontological argument next. ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [March 8, 2005, 8:36pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/352 "2005-03-08T20:36:01Z")
> [@](#): > > Was so! The image wasn’t imaginary but the can was, is and will be until Darth Vader is not fictional. To say otherwise is to fall into Liberal’s game. You’ll be agreeing with the ontological argument next. Maybe I didn’t explain it well enough in my OP. Darth + watering can in my mind, or on Photoshop, _could_ comprise images comprising photons directly from the watering can and the actor in the Darth costume themselves. They would not then be images of imaginary objects. Of course, _my_ memories I’m Photoshopping aren’t quite so: Of Darth, mine is a photograph of a photograph. Of the watering can, mine is a kind of “average” or “stereotype” of all the watering cans I’ve seen. This process of _copying_ memory might at first seem a little confusing in terms of physicality, but so long as one understands that photons are physical too, I don’t think there’s a fundamental problem. ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [March 8, 2005, 8:53pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/353 "2005-03-08T20:53:21Z")
> [@Arwin](#): > > The blind man would not see the wall either. Of course, but I did not offer his blindness as evidence that the image isn’t there, but that it is perceived as distinct from the wall (even though it isn’t) by sighted men. Were the wall and the image distinct objects in space-time, he ought at least to be able to feel them. He can feel that the wall is not the air, for example. > [@](#): > > Just grabbing a random definition of this kind of image from a web-dictionary: Interestingly, that’s the same definition that Other-wise and I are using for the immediate memory image, and apparently from the same source. > [@](#): > > We observe physical objects visually by their reflections striking our eyes. In that sense, we really see the wall in pretty much the same way as we see an image projected onto that wall. In the case of seeing the wall by itself, we see the wall by virtue of the light that is already present and is bounced back to us in a particular way by the wall. Already present? What do you mean? There is light from a variety of possible light sources (the sun, for example) illuminating the wall, but the wall is not illuminating itself. There is no light “already present”. A projection is nothing more than more and/or different light. > [@](#): > > In the case of an image projected onto the wall, we see the light of, say, a table, projected onto the wall, and reflected back towards us. Our seeing is the physical reception of light. Every reflection of light is from physical objects. Nothing there I disagree with. 🙂 In fact, the whole wall is doing the same thing you describe the image as doing — bouncing back light. The image is just PART OF the light bouncing off the wall. > [@](#): > > If I were to object to calling everything physical, I would rather say that every object or entity we choose to distinguish from that light-fest, whether it is the wall, or the image, or the combination, or the table in the image, or the table in front of the wall, or the projector, is a mental construct, abstraction, or whatever. If we consider everything that goes on in the mind as physical too, then it is. If we don’t, it isn’t. I’m afraid that the excluded middle does not apply here, mostly because of the ambiguity of the term “mind”. If you mean brain, then certainly everything that goes on in the brain is physical. But the image on the wall isn’t even the same as the image in your brain. Let’s select an image of arbitrary complexity, say, the aforementioned WWII battle scene. So long as the image on the wall is being projected, you can point to the wall and tell me exactly how many centimeters the tiny tank in the background is from any edge of the image. But if the image is sufficiently large, you do not even see the whole image when you look at that portion. Your field of vision is very narrow, and your brain is filling in the rest as best it can. And once you take your eyes off the image, you are practically helpless to provide the kind of detail you can provide from the image on the wall. > [@](#): > > At this point, we’re getting to the point where you should rather to determine which approach is more useful than which approach is more real. Or rather, realise that thanks to the skeptics, nothing shapes reality other than our own subjective value assignment, objectified only by having more people agree with you on that value assignment. Certainly, everything inside a man is subjective. But I disagree that objectivity is born of consensus. It is born of accessibility relations among frames of reference. Or as Arthur Eddington put it: “Reality is only obtained when all conceivable points of view have been combined.” ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [March 8, 2005, 8:57pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/354 "2005-03-08T20:57:34Z")
> [@Hoodoo Ulove](#): > > To say otherwise is to fall into Liberal’s game. I’m afraid you have me at a disadvantage. What game am I playing? ---
**Author:** ![Hoodoo\_Ulove](https://avatars.discourse-cdn.com/v4/letter/h/58956e/32.png) [@Hoodoo\_Ulove](https://boards.straightdope.com/u/Hoodoo_Ulove)\ **Post date:** [March 8, 2005, 10:14pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/355 "2005-03-08T22:14:15Z")
> [@Liberal](#): > > I’m afraid you have me at a disadvantage. Im my dreams. [QUOTE=Liberal] [QUOTE=Liberal] > [@Liberal](#): > > The physicalist will argue that perception emerges from the physical and is therefore physical. But there again, there is the presumption that physical is everything conceivable plus everything that isn’t. I was disputing the view that “everything is physical”, giving an example of Mr. Vader’s green can. I felt it was injudicious to say that “Darth Vader’s green watering can” is physical. > [@SM](#): > > Maybe I didn’t explain it well enough in my OP. Darth + watering can in my mind, or on Photoshop, could comprise images comprising photons directly from the watering can and the actor in the Darth costume themselves.\*\* They would not then be images of imaginary objects.\*\* Agreed. But although the image of the can in your mind or in Photoshop got there by purely physical processes, the can is imaginary. If not, where is it? I.m sure it would not fit inside your skull. ---
**Author:** ![Arwin](https://avatars.discourse-cdn.com/v4/letter/a/51bf81/32.png) [@Arwin](https://boards.straightdope.com/u/Arwin)\ **Post date:** [March 8, 2005, 10:20pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/356 "2005-03-08T22:20:04Z")
> [@Liberal](#): > > Of course, but I did not offer his blindness as evidence that the image isn’t there, but that it is perceived as distinct from the wall (even though it isn’t) by sighted men. Were the wall and the image distinct objects in space-time, he ought at least to be able to feel them. He can feel that the wall is not the air, for example. That’s why I said it doesn’t matter in the end. It’s all a spectacle of light travelling and reflecting on matter, some of which is caught by the human eye and transmitted to the brain, where it is interpreted. > [@](#): > > Already present? What do you mean? There is light from a variety of possible light sources (the sun, for example) illuminating the wall That is exactly what I meant. > [@](#): > > I’m afraid that the excluded middle does not apply here, mostly because of the ambiguity of the term “mind”. If you mean brain, then certainly everything that goes on in the brain is physical. But the image on the wall isn’t even the same as the image in your brain. Let’s select an image of arbitrary complexity, say, the aforementioned WWII battle scene. So long as the image on the wall is being projected, you can point to the wall and tell me exactly how many centimeters the tiny tank in the background is from any edge of the image. But if the image is sufficiently large, you do not even see the whole image when you look at that portion. Your field of vision is very narrow, and your brain is filling in the rest as best it can. And once you take your eyes off the image, you are practically helpless to provide the kind of detail you can provide from the image on the wall. I don’t see the relevance of this, though. The whole interaction remains a physical one. I see no evidence of the contrary and there is nothing in this world that leads me to believe there is anything else, nor have I ever encountered anything to falsify that presumption. If I followed the discussion you had with **SentientMeat** correctly, you take another position on this, and I apreciate that, but I don’t think we’ll ever even get near a consensus on this level. At best, we can agree on some levels of abstraction - but everything is physical, takes place at a physical level, and can ultimately be explained by deconstructing the complex arrangement of particles and their movement. > [@](#): > > Certainly, everything inside a man is subjective. But I disagree that objectivity is born of consensus. It is born of accessibility relations among frames of reference. Or as Arthur Eddington put it: “Reality is only obtained when all conceivable points of view have been combined.” It’s only a very subtle difference, but I appreciate it. Of course I meant that all conceivable points of view would include that of other observers, but also everything else you can get at - as many of your own senses as possible, x-rays, etc. We’d prefer the crew of observers to use as many frames of reference as possible, because we have experiend that contributes to the predictability of the theories we devise to describe the world. However, noone is ever truly objective, for there is no collective consciousness that transcends the objective (yet anyway - who knows what will happen one day in the future), and so the individual remains the smallest, most limiting part in the whole, for now. Culture, perhaps, transcends the individual, but there is nothing transcending the individual yet to appreciate culture at more than a subjective level. 😉 ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [March 8, 2005, 10:28pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/357 "2005-03-08T22:28:41Z")
Question for the general table: An image is projected onto the surface of quasar APM08279+5255, the most luminous object in the universe, somewhere between 4 and 5 million billion times brighter than the Sun. Is it the case that there is an image on the wall dinstinct from the wall but not an image on the surface of the quasar? ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [March 8, 2005, 10:35pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/358 "2005-03-08T22:35:40Z")
> [@Arwin](#): > > That’s why I said it doesn’t matter in the end. It’s all a spectacle of light travelling and reflecting on matter, some of which is caught by the human eye and transmitted to the brain, where it is interpreted. But that’s the whole of nature. Neither the image nor the wall is dinstinguished in that regard. > [@](#): > > I don’t see the relevance of this, though. The whole interaction remains a physical one. I see no evidence of the contrary and there is nothing in this world that leads me to believe there is anything else, nor have I ever encountered anything to falsify that presumption. If I followed the discussion you had with **SentientMeat** correctly, you take another position on this, and I apreciate that, but I don’t think we’ll ever even get near a consensus on this level. At best, we can agree on some levels of abstraction - but everything is physical, takes place at a physical level, and can ultimately be explained by deconstructing the complex arrangement of particles and their movement. It is relevant because you suggested that everything that goes on in the “mind” (an ambiguous term) is physical. I suggested that you might mean the brain, in which case the image on the wall is not the same as the image in your brain. Therefore, your brain is not representing physical reality to you. A brain examining nature is akin to an axiom that begs its conclusion. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [March 8, 2005, 10:52pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/359 "2005-03-08T22:52:07Z")
I’m answering this without reading all the stuff that has been posted since, but I’ll get to that. > [@Liberal](#): > > But the massless photons eminate _from the wall_. There has to be an electron whose orbit collapses. And the electron has to be a part of an atom (in the physics sense). The image is merely _a part of the wall_ that is emitting photons that correspond to points in the image. The _whole wall_ is emitting photons. > > All that is to say that the image is merely a perception of the wall. You are not claiming the image **is** the wall, surely. And the characteristics of the photons being ejected from the wall (which I took into account in my post) are changed depending on if there is a picture being projected, a light shone, or nothing impinging the wall except room light. I was using image as the wavefront of photons from the wall, that could be intercepeted by our eyes or by a camera. If you mean by perception the model of the wall in our brain, that is a different story indeed. The image might be changed by our internal processing. A color blind person might see the color wrong, etc. > [@](#): > > If you put a blind man in front of the wall, he will perceive no image. He might perceive a bit of heat as the light heats the wall, but that’s it. You could give him the same effect by using a torch on the opposite side. It is the wall that is physical; the image is just a perception. Aha, I was right. 🙂 Now, here’s where the definition part comes in. The physicalist will declare that perception is physical too. But that’s only because he has taken as axiomatic that anything you name is physical. It is a system built on a conclusion as a premise. Now, I believe that God exists, but I am scrupulously avoiding any and all metaphysical references as we examine this issue of physicality. If we’ve already postulated that all things are physical, then what are we doing here? We need only a simple syllogism: all things are physical; an image is a thing; therefore, an image is physical. Done. End of story. There is an OP, and possibly one or two replies of “Yep,” “Uh huh”, and “You’re so right.” [/quote] We don’t have any evidence whether god is physical or not, assuming he exists. Do you consider the raw image, composed of photons, physical? (I bet this has already been asked.) > [@](#): > > But if we are going to show whether an image is physical, then we do not start with the premise that it is. It seems to me that to be physical, something ought to be made of physical stuff — elementary particles, strings, or whatever. Or, in terms of spatial-temporal, it ought to be distinguishable from all other spaces and times. The physicalist will argue that perception emerges from the physical and is therefore physical. But there again, there is the presumption that physical is everything conceivable plus everything that isn’t. > > To test the tautology of physicalism, propose this question: If the metaphysical God exists, is He physical? If the physicalist answers yes, then he has defined physical as everything that is proposed, even contradictions. If he answers no, then he has admitted that physicalism is false. I have often scolded materialism as the most logically difficut position to hold, but its spawn, physicalism is more difficult yet. The physicalist must posit either one of two things: (1) contradictions exist, or (2) I’m wrong. There are other answers. First, the world is physical so no god does exist. (You areasking a physicalist to posit that physicalism has been refuted, and then you say _hah!_ As for me, I have no answer until I see evidence of god. I do have evidence of images and perceptions. And the question is: do you consider a manufacturing process physical? A manufacturing process is not made of elementary particles, it is not something you can hold. The answer to this question will tell if we are talking at cross-purposes. Manufacturing processes are a lot easier to discuss than images or perceptions. > [@](#): > > If you wish. But so is the wall. Photons are coming from all over it. You’re merely selecting those photons to which your brain has assigned a perception born of familiarity with other things. You’re simply going, “Hmmm… that portion of the wall that depicts a battle from World War II is familiar to me, not as a wall, but as a battle from World War II.” Sure. The photons get interpreted all sorts of ways. The model built in your brain from them is neither the wall nor the photons, it is a function of the photons (and not even the wall, since you see only the image of the wall, not the wall itself.) ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [March 8, 2005, 11:07pm UTC](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584/360 "2005-03-08T23:07:54Z")
> [@Liberal](#): > > Question for the general table: > > An image is projected onto the surface of quasar APM08279+5255, the most luminous object in the universe, somewhere between 4 and 5 million billion times brighter than the Sun. Is it the case that there is an image on the wall dinstinct from the wall but not an image on the surface of the quasar? There is an image coming from the quasar (assuming that the image was reflected from its surface) consisting of a set of photons. (Maybe a wall illuminated by a very, very bright light and a very dim image would be a better example.) But there is no image in our brains, since the physical limitations of our eyes would lose the photons from the image amongst the photons from the quasar. We would not perceive this image. As for the photons be emitted from the wall - if you shot a bullet into the wall, are the particles of wallboard that fly out still the wall, or something (obviously physical here) emitted from the wall and now different? As for Darth’s watering can - that can be answered through general semantics. The image of the can is a tag for a non-existent thing. If I write “Invisible Pink Unicorn” on paper, the words are physical (as pencil markings) but the IPU does not become physical by my creating a tag for her. [Previous page](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584.md?page=17) [Next page](https://boards.straightdope.com/t/a-memory-is-a-physical-thing/292584.md?page=19)