A new (at least I think it is new) objection to the DA just occurred to me (googling computational + irreducibility +doomsday came up blank).
This objection (unfortunately) requires a few assumptions: 1) No "block" universe (ie. the universe is a process). 2) Wolframian computational irreducibility ((2) may be a consequence of (1) under certain other assumptions) 3) No backwards causation. The key argument is that by 1) and 2), at time T, the state of the universe at time T+x is in principle un-knowable, even to the universe itself. Thus, at this time T (now), nothing, even the universe itself, can know whether the human race will stop tomorrow, or continue for another billion years. To accept the DA under these conditions requires accepting backwards causation; that the probability for my existence must depend on a fact determined in the future. If we wish to accept the DA is possible, we must deny at least one of the above three. The following thought experiment illustrates the argument: Imagine I know that I am one of the first ten humans that God has created (I know this, because God has told me). I also know that God is in the process of throwing a dice (say the dice are tumbling end-over-end but have not landed yet). Neither God (nor the universe, if the two are not equivalent) knows what the dice result will be before it occurs (it is unknowable by (2)). If the dice comes up heads, God will create a billion more people (so she says, anyway). If the dice is tails, God will create no more people. Should I be able to predict that the dice will come up heads? I'd argue that given 1), 2) and 3), our situation is analogous to the above; and that no, contra the DA, we should not be able to predict that the dice will come up heads. Its not a slam-dunk against the DA because 1), 2) and 3) are far from uncontroversial; but it *seems* to be a hit. Then again, the DA is a slippery weasel and I expect there's probably some counterargument somewhere. Perhaps God can change her mind? Jonathan Colvin
