Of course, what is moving and what is fixed depends on the point of reference. In my analysis, I take the present as the fixed point of reference. When I vary the unknown Y, I am varying the unknown number of years ago when the last asteroid strike occurred. The time when the asteroid destroyer is built remains fixed at 150 years after the present.
Keep in mind the first error I noted in my post. Leslie starts with prior information and prior probabilities about future births, not total births. Leslie assumes that mankind will be able to colonize the galaxy 150 years—equivalently, roughly 20 billion births—from now, regardless of how many unknown births have already occurred.
What I would like to see (among other things) is …
I am new to Less Wrong, and so I’m not as familiar as you are with how things are done on this site. Manfred, I do appreciate your comments and your interest in my thesis. But I think that, at some point, scholarship demands that you turn to original sources, which in this case include my e-book. If I thought I could give a complete argument in a discussion post, I would not have written a whole book. Rather than my trying to recapitulate the book in a haphazard order and with impromptu formulations based on your particular questions, don’t you think it would be more productive for us to refer to the book? Or at the least, you could refer to my published paper (upon which the book is based), which is part of the peer-reviewed literature on the subject. The book is clearer than the paper though, and I have already offered the book to LWers such as you for free. (Only one LWer has taken me up on the offer.) The book is only 22,000 words long, and I think you would have little trouble homing in on the sections and formulations that interest you most.
I appear to be using a different meaning of “self-sampling assumption” than you. Rather than worrying about it, do we agree that when used correctly it’s just an expression of underlying statistics?
If it were used ‘correctly’, yes, SSA would just be one perspective on the prior information. But I know of no real-life applications of the Doomsday Argument in which SSA has been used ‘correctly’.
Added 8/19/2011: On second thought, I really do not know what you mean by this statement without your providing context. I think SSA is wrong, at least as it has been used in the Doomsday Argument; I don’t know what it would mean to use correctly something that is wrong. To be as charitable as possible, I could say that if the mathematical formulas implied by SSA happened to match up with the prior information in a given case (and I have never seen such a case related to DA), then SSA would just be one perspective on the prior information.
Your comment touches on the crux of the matter.
Of course, what is moving and what is fixed depends on the point of reference. In my analysis, I take the present as the fixed point of reference. When I vary the unknown Y, I am varying the unknown number of years ago when the last asteroid strike occurred. The time when the asteroid destroyer is built remains fixed at 150 years after the present.
Keep in mind the first error I noted in my post. Leslie starts with prior information and prior probabilities about future births, not total births. Leslie assumes that mankind will be able to colonize the galaxy 150 years—equivalently, roughly 20 billion births—from now, regardless of how many unknown births have already occurred.
I am new to Less Wrong, and so I’m not as familiar as you are with how things are done on this site. Manfred, I do appreciate your comments and your interest in my thesis. But I think that, at some point, scholarship demands that you turn to original sources, which in this case include my e-book. If I thought I could give a complete argument in a discussion post, I would not have written a whole book. Rather than my trying to recapitulate the book in a haphazard order and with impromptu formulations based on your particular questions, don’t you think it would be more productive for us to refer to the book? Or at the least, you could refer to my published paper (upon which the book is based), which is part of the peer-reviewed literature on the subject. The book is clearer than the paper though, and I have already offered the book to LWers such as you for free. (Only one LWer has taken me up on the offer.) The book is only 22,000 words long, and I think you would have little trouble homing in on the sections and formulations that interest you most.
If it were used ‘correctly’, yes, SSA would just be one perspective on the prior information. But I know of no real-life applications of the Doomsday Argument in which SSA has been used ‘correctly’.
Added 8/19/2011: On second thought, I really do not know what you mean by this statement without your providing context. I think SSA is wrong, at least as it has been used in the Doomsday Argument; I don’t know what it would mean to use correctly something that is wrong. To be as charitable as possible, I could say that if the mathematical formulas implied by SSA happened to match up with the prior information in a given case (and I have never seen such a case related to DA), then SSA would just be one perspective on the prior information.