> that people go to sleep all the time and wake up, and remain the same person
You have absolutely no way of knowing that last part is true. You can only see their behavior, which is identical whether they are the same consciousness or a different one from the one it was yesterday. You don't even know whether they have any conscious experience at all.
> And I know (for practical purposes) I do the same.
You do not. The "for practical purposes" points at your _body_. There is no evidence that an organic body is in any way special. If you upload your consciousness and the resulting computer 'body' works as a normal body, it _will_ generate a consciousness and that consciousness _will_ feel that it is 'you' (itself). Note that we're talking about hypothetical practically perfect computer bodies (which may be completely virtual, as longs as its sensors and actuators live fully in that virtual world).
You can spin the illusion of a continuous conscious experience every way you want. It is still just that, an illusion.
> You can only see their behavior, which is identical whether they are the same consciousness or a different one from the one it was yesterday.
The first clause of the sentence is true, but the second is not.
You never directly see a thing itself, you only ever see its effects on the world. You rationally postulate the presence of water because of its clear colour, its hydrating effect on you, its tendency to become a gas at 100C, its tendency to dissolve salt, and so on. Similarly, you rationally postulate the presence of the same person, at 10pm on Monday and 7am on Tuesday, because he has the same personality, the same look, the same eye and hair colour, the same body shape, etc. We know about the presence of a thing from the presence of its effects and behaviour. If these remain the same, it is rational to believe that the person remains the same.
> You don't even know whether they have any conscious experience at all.
Again, knowledge of effects leads to knowledge of the thing causing said effects. I am aware of my own conscious experience, I see Bob affects the world in ways that are very similar to myself and other human beings, and so I rationally postulate that he is a conscious, rational being like I am. You never see a person's mind directly, but you see the effects of the person's mind the whole time. You see such effects through their body. If the effects remain the same, or change only in certain, limited ways, it's reasonable to believe that the cause remains the same (and frankly crazy to believe otherwise).
> The "for practical purposes" points at your _body_. There is no evidence that an organic body is in any way special.
The mind and the body form one substance. The idea that "my mind is one thing, my body another" has been tried and failed as a philosophical idea several times in history. It raises far more problems than it purports to solve. I know I continue through time in part because my body continues through time. You say the body isn't "special"; I don't know what this means, but I know my body, and other people's bodies, are different from other things, because they walk, talk, reason, sense, desire, and so on. (Once again, the effects and behaviour of a thing lead us to knowledge of that thing.) The idea that consciousness or self can be 'uploaded', even in theory, is pure fantasy. You and your body are one thing.
> You can spin the illusion of a continuous conscious experience every way you want. It is still just that, an illusion.
If this is so, explain how rational thought is possible. Given that rational thought involves you reasoning from A to B to C through time, how is this possible if there is no continuous 'you' that is going through time?
You have absolutely no way of knowing that last part is true. You can only see their behavior, which is identical whether they are the same consciousness or a different one from the one it was yesterday. You don't even know whether they have any conscious experience at all.
> And I know (for practical purposes) I do the same.
You do not. The "for practical purposes" points at your _body_. There is no evidence that an organic body is in any way special. If you upload your consciousness and the resulting computer 'body' works as a normal body, it _will_ generate a consciousness and that consciousness _will_ feel that it is 'you' (itself). Note that we're talking about hypothetical practically perfect computer bodies (which may be completely virtual, as longs as its sensors and actuators live fully in that virtual world).
You can spin the illusion of a continuous conscious experience every way you want. It is still just that, an illusion.