I haven’t read the whole essay, but the portion that you quoted isn’t an argument from incredulity.
An argument from incredulity has the form “Since I can’t think of an argument for assigning P low probability, I should assign P high probability.”.
Aubrey’s argument has the form “Since I can’t think of an argument for assigning P low probability, I shouldn’t assign P low probability.”.
He’s expressing incredulity—and then arguing from that. He goes on to assume that this “singularity” thing happens for much of the rest of the paper.
I haven’t read the whole essay, but the portion that you quoted isn’t an argument from incredulity.
An argument from incredulity has the form “Since I can’t think of an argument for assigning P low probability, I should assign P high probability.”.
Aubrey’s argument has the form “Since I can’t think of an argument for assigning P low probability, I shouldn’t assign P low probability.”.
He’s expressing incredulity—and then arguing from that. He goes on to assume that this “singularity” thing happens for much of the rest of the paper.