I have several problems with Kastrup’s argument, although I agree with his conclusion. Which means that I use a different argument to get to a similar conclusion. I agree that arguments about the “pixelization” of perception do not necessarily transfer to the “pixelization” of the perceiver. However, he appears to take this as an argument that the perceiver cannot be pixelized, which goes too far in my opinion. Or he simply states it without offering any proof at all. Instead he presents the argument that the simulated is not the thing being simulated. Again, I agree with that argument. But then he seems to say that because that is true, consciousness cannot be generated from constituent parts… Or something - I find his argument muddled.
There is a way to have a progressive aggregation argument that is more like biological cells than like pixels or subatomic particles. So, biological cells on their own have pretty limited behaviours, but when they are organized into coherent structures, the behaviour of the whole may be very different from the behaviour of the individual cells. I am not talking about animals per se, but, for example, animal organs - the heart has a complex set of properties and functions that in some sense include emergent properties that the individual cells do not have. There is some kind of a threshold above which a complex celled entity can function and maintain itself (in relation to its environment, of course, never separately from the latter) but below which the sophisticated behaviour is lost. When a heart stops pumping, it doesn’t mean its constituent cells die immediately - they eventually will because they lack the resources they need to continue. So a certain kind of “experience of life” may be viewed as being “constructed” from component parts in such a way that emergent properties confer a more sophisticated experience of life. Note that this is an argument that Kastrup negates, in a sense, and yet which also leads towards a comparable conclusion for other reasons. Instead of rejecting the idea that consciousness can be “downloaded” into an appropriately designed artificial structure because experience cannot be fragmented into pieces (which is how I understand part of Kastrup’s argument), the alternative reason is because experience requires emergent properties of a particular kind (indeed, of the living, embodied kind), and artificial structures made from inert matter cannot generate the right kinds of emergent properties. This would suggest that one might be able to “create” organic structures that did have the right kind of emergent properties to produce consciousness. We do not have the means to test such an idea today, but, as a scientist, I prefer arguments that can be tested over arguments that cannot (I do not know how to test the idea that consciousness cannot be broken into pieces…). And it seems to me it might be true that one could “create” or “design” a conscious being out of organic components and behaviours rather than inorganic components. Maybe… This still does not mean one could be able to “download a consciousness from one organic living body into another” - that would depend on the details of what emergent properties are needed to generate consciousness, another question we are unable to answer at the moment. Furthermore, the argument about embodiment is that the specifics of a particular body matters - that is, the embodied hypothesis of consciousness is that a given body may generate a single and unique consciousness. If that is the case, then you cannot simply “transfer” consciousness from one body to another - it doesn’t work like that at all.
Furthermore, although individual cells don’t have the same life experiences as complex cell ensembles which include sophisticated and emergent behaviours, yet, as individuals, they may be said to have some kind of “life experience”. The critical distinction here is the existence of emergent properties and their role as a manifestation of a kind of “complexity threshold” (which is what Teilhard talked about - nobody talked about emergent properties in his day). Is consciousness an emergent property of certain kinds of life forms? That is the question we should be asking, not whether subatomic particles have some kind of “microconsciousness”… However, the same kinds of questions also were once applied to the emergence of life from inert matter, and the science seems to suggest that life IS an emergent property of certain kinds of macromolecules. Kastrup says that is an argument for biology, and he is again correct, but that does not mean it is not also an argument for consciousness if the two levels of argument are linked together…