Since we behave no differently, and assuming we never will, there is no possibility of us being able to determine whether or not we perceive them differently. Hence it is not possible to demonstrate truth and falsity of any assumption on the subject and as such it is not science.
Right, you will never be able to
tell whether you perceive them differently or not. But
truth has not nothing to do with that. It can still be
true that you perceive things differently, even if you can never tell, and even if it makes no difference to how you behave.
To illustrate, suppose you had a race of sentient but rather stupid creatures who were, intellectually, completely incapable of working out whether the proposition "If A and B are different names for the same object, then anything which is true of A is also true of B" is true or not. Whether or not it is true, they get on with their lives in exactly the same way. But it doesn't follow from that that the proposition has no truth value.
In other words, you keep talking about what we can "determine" or "demonstrate", or "observe", or "manipulate", in an "operative" way. But none of those things has got anything to do with truth - they're all pragmatic considerations, concerned with what we can know and what use it is to know it.
Well do I personally notice this? If I do notice it and am distraught about it then there has occured an observable phenomenon, in contrast to the above point. (At the very least I should speak to a doctor)
Say your memory is altered at the same time, so you don't remember perceiving things any differently. It still seems very clear to me that something would still have changed. You might never know it, and it might make no difference whatsoever to your behaviour, but it would still be true that you had changed. It just wouldn't be
knowably true.
This illustrates the difficulty of constructing a theory given only one observation of the phenomenon (i.e. the history of the universe up until that point). If it were possible to reboot the universe and reobserve it many, many times then someone might start to discern differences.
I meant two theories that give the same results, given many observations.
Well, say that in this example they do. Say that these are completely deterministic universes, and that everything in them happens the same way every time you "boot" them, including the behaviours of the various deities. And say we have some external observer who can watch what happens over and over again, but who can't observe the deities themselves. Would you still say that, for this observer, the two rival hypotheses are actually the same hypothesis?
But there would be absolutely no disadvantage for the rest of the world if they just kept on believing that I hadn't been annihilated and respawned. As long as my clone behaved the same in every future event as I would have, then yes, nothing has changed. Again this was an isolated event. If it started happening all the time, all kinds of issues crop up. How long is "the instant"? Are there measurable abnormal phenomena that occur during a swap etc.
Of course there would be no disadvantage or advantage for the rest of the universe, whichever hypothesis they believed. But how can you infer from that that there is no difference whatsoever between your own continued existence and your annihilation and replacement with a clone? Of course something has changed - you don't exist any more! Suppose that the moment of swapover is completely undetectable. And suppose that it could, in principle, be happening all the time. According to you, to say that this happens all the time
is exactly the same thing as to say that it never happens. And if that is true, it would be
just as reasonable to say that it happens all the time as it would be to say that it never happens at all. But that seems very peculiar!
For all constructive purposes it is. If you were a cosmetics company, you might consider employing someone who can intuitively design "nice smells" out of their extensive experience with scents. On the other hand it would be equally ok to hire someone (who was born without a sense of smell) who can reach exactly the same results using advanced theoretical models and computer simulations of how people would react to the smells. As long as the results are 100% identical.
Cunning, but I think this fails even by your own standards. From the point of view of the person in question, there could be a big difference between having no sense of smell but an amazing knowledge of chemicals and having a good sense of smell. So there'd be an observable difference, even if they are the only person who can observe it. Which suggests again that it's begging the question to assume that there would be
no observable difference - just as it's begging the question to assume that the observability of difference is the definition of truth.
I suppose I was merely trying to criticize the "angels on pinheads" types of discussions that non-scientific reasoning can lead to w.r.t. questions about "the universe". I suppose the field is fraught with the danger of mixing up perception with cause and effect and never cleanly separating out what it is that is being discussed. But I won't argue this point too much as I'm sure that not all philosophers make this mistake (To be clear: I'm not saying that anyone here has done that)
That's fair enough, although I don't really see what's wrong with "angels on pinheads" discussions anyway (not that that discussion ever occurred anyway, of course). I should hope that philosophers would confuse perception with cause and effect
less than other people, not more - certainly the nature of causation is one of the perennial topics in philosophy, at least since Hume.
