1) Uncertainty is not of itself a mark of intellect; it is the acknowledgement of uncertainty that is the mark of intellect. (e.g. look at, for example, a good statistical model - there's X% chance of this happening, Y% chance of that happening, and a margin of error for each percentage). For example, we acknowledge that it is possible that all of our laws of nature apply only locally; however, as observations of the universe as a whole are, by and large, consistent with the laws of nature we have observed, it is more plausible (>99%) to say that, with our current level of knowledge, the universe's laws are consistent with what we observe locally. 2) Your point that "We cannot be certain of X" rings fundamentally of shifting the burden of proof. We have solid evidence that "X is true". You say "But X might not always be true. You have not fundamentally assessed every single possible situation where X could occur and not be true". You can *never* consider every single possibility once a certain level of complexity is breached. Paraphrasing the essence of Null's post [as I saw it]: If you don't accept X because you cannot be 1.000....00000 certain that X is true, then you are not being smart, you are just stating "I do not want to be wrong in the 0.0...001 event that this is wrong". For example - newton's laws are *wrong* over the universe, but they're almost perfectly accurate over 90% of situations we deal with.