Re: Re TimeTravel

Hal Finney (
Fri, 23 Oct 1998 10:47:48 -0700

Brian D Williams, <>, writes:
> You are arguing that because no one has come back from the future
> that it proves time travel (backward) is impossible. I merely
> stated the obvious, the reason no one has come back from the future
> isn't that time travel (backward) is impossible (although I believe
> it is.) it's that the future hasn't happened yet.

I don't quite understand how this argument works.

Suppose we wait until the future happens (so to speak!), and someone invents a time machine that allows travel into the past. I gather that you think that is at least logically possible.

Now we travel into the past, back to good old 1998, and here we meet Brian D Williams. We introduce ourselves to him and say that we are from the future and that we've come back in a time machine to visit him.

He says that is impossible, because the future hasn't happened yet, and shows us his message which he had just sent off to the extropians list.

Obviously he is wrong in some sense, because he concluded that time travel was impossible, yet it was possible, and we are there. What is wrong with his argument?