5th
Ok, the familiar anthropic principle – specifically the version you defined - begins in the past and projects forward in time.
Someone says: “Isn’t it incredible that we should find ourselves in exactly the right conditions suitable for human life! The chances against it were astronomical!”
The quantum anthropicist replies: “No. All possible histories get played out. It was always 100% certain that we could only find ourselves in those conditions suitable for human life. Admittedly, the states of reality where we don’t exist vastly outnumber the ones where we do, but that needn’t trouble us. Starting from the Big Bang, the chance of us finding oursleves in any state of reality where we did’nt exist was always 0%.”
Ok, that’s the forward anthropic principle, which you already know. Now for the same principle applied backwards. It’s purpose is to justify the validity of memories and history. Here is an exchange between a quantum sceptic and a reverse anthropicist.
Quantum Sceptic: “How do I know that we all didn’t come into existence five minutes ago, along with false memories of a history?”
Reverse Anthropicist: “Because all possible histories that lead to this moment exist.”
Quantum Sceptic: “But suppose we did’nt exist in the vast majority of those histories?”
Reverse Anthropicist: “It makes no difference.”
Quantum Sceptic: “Why not? Quantum indeterminacy demands that we define reality according to the majority of possible states.”
Reverse Anthropicist: “If at least one history coincides with our consensus memory, that means we have a real history and our memories are not false. Given, that we remember existing, and given that there is a single history which corresponds to our memory, then it is 100% certain that we did exist. Starting from the present and working backwards, the chance of us finding oursleves in past states where we didn’t exist is always 0%. Our history is simply applicable to those past states in which we did exist, no matter how few there are.”
That is my ‘reverse anthropic principle’.
