For all practical purposes, yes. There are things that we know, the negation of which would contradict such a tremendous portion of our experience that even the possibility of being wrong would imply that the universe is without rules. For example: The sun appears to set to the west of where it appears to rise (in places between the arctic and antarctic circles). Live humans usually breathe air. A die, each roll of which is independent and has a 1/6 chance of yielding a "three," rolled three times, has a 1 in 216 chance of yielding a "three" for all three rolls. Not only do we consider the probability that such things are wrong so low as to be negligible, we are incapable of acting in accordance with the possibility that each such thing might be wrong. If you have watched the grinding of the coffee beans and the brewing of the coffee, do you stop in the middle of drinking, put down the mug, and check to see that the coffeepot wasn't a figment of your imagination? And check again to catch a possible deception of senses or memory from the last time?
Can we, in general, trust our senses? How do we know that the world we see isn't a horrible misinterpretation of the reality around us? Easily: Natural selection did not kill us off. Our senses are evolved to give us information about the world, so that we could react to it appropriately. If they were not mostly trustworthy, we could never have survived.
But what about Cartesian demons1? Could I be a brain in a vat, being fed a bunch of fake sensory information, with a computer extrapolating the effects of my "actions" on its virtual world? Could I be trapped in The Matrix? Or worse, could I be trapped in a version of my short story, "Life," and not exist at all, outside of the manipulation of numbers within a computer? Of course I could. But all that would mean is that the universe within which I operate is not considered the "real" world by those beings outside of it. Knowledge is not guaranteed to apply to any universe beyond that in which it is gathered. Within this universe, which is the only one that matters for the purpose of my gathering information and reacting appropriately, that which I know to be true is valid and correct. The possibility of higher realities does not itself change the validity and utility of this knowledge, as applied within this universe. (It does, on the other hand, introduce the possibility that someone outside might tamper with this reality. (This sort of event is known in some circles as a "miracle".) In that case, their propensity to tamper constitutes part of the "rules" of this universe.)
"Still," comes an objection, "you never know everything. There is always the possibility that you are missing information which would change your mind." Well, no. There isn't always. "Sufficient data" does not require "exhaustive data". For example: If you know that the blue house and the red house are occupied, one solely by Mr. Smith, and one solely by Mr. Jones, and you know that Mr. Jones occupies the red house, you have enough information to figure out that Mr. Smith occupies the blue house. You do not need to also know all about Mr. Smith's stamp collection. So long as the axioms, evidence, and deductions are sufficient to constitute proof, contrary information cannot exist.
"But," cry the objectors, "given that there are plenty of people who claim to be positive of something, but turn out to be wrong, how can you be sure that you are not similarly mistaken?" I will surely grant the premise; most people are far too willing to proclaim certainty in uncertain circumstances. But the existence of unjustified certainty in no way disproves the possibility of justified certainty. It does at least imply that merely being certain is no proof.2 But as the reliability of the believer's system of evaluation and reasoning changes, so does the justification for their certainty.
1. I find it mildly irksome that Descartes' name is attached to a concept proposed by people of far more sound reasoning than his, due to his over-popularized attempt to disprove that concept.
