Unknown: I think that you are using against Eliezer a basic heuristics and biases fallacy that he used, repeatedly and frustratingly, against me back before he learned, from Robin, that knowing about biases can hurt you as a rationalist http://lesswrong.com/lw/he/knowing_about_biases_can_hurt_people/. Every proposition can be converted into an arbitrarily long conjunction. That fact plus the fact that certain people participating in some psychology experiments failed to meaningfully give certainties much greater than 85% does NOT justify your converting any statement that you disagree with, or by anyone you wish to take status from, into an arbitrarily long conjunction as a valid method of lowering its probability to arbitrarily close to zero. This habit is a form of intellectual suicide that closes you off to conflicting opinions or information.

BTW, In actual fact, people make true mathematical proofs with thousands or tens of thousands of steps. Outside of math, and even in math, it is best to independently ground each conclusion with multiple parallel evidential pathways, but doing so is not strictly necessary if one is sufficiently careful.