With the (important) proviso that "knowledge", "trustworthy", and "are true" need to be qualified with something like "approximately, kinda-sorta, most of the time", I think these premises should be assumed as working hypotheses on the grounds that if they are badly wrong then we're completely screwed anyway, we have no hope of engaging in any sort of rational thought, and all bets are off.
Having adopted those working hypotheses, we look at the available evidence and it seems like it fits them pretty well (note: this isn't a trivial consequence of having taken those things as working hypotheses; e.g., if we'd assumed that our perception, reasoning and memory are perfectly accurate then we'd have arrived quickly at a contradiction). Those propositions now play two roles in our thinking: as underlying working assumptions that are mostly assumed implicitly, and as conclusions based on thinking about things as clearly as we know how.
There's some circularity here, but how could there not be? One can always keep asking "why?", like a small child, and sooner or later one must either refuse to answer or repeat oneself.
Somewhat-relevant old LW post: The lens that sees its flaws. My memory was of it being more relevant than it appears on rereading; I wonder whether there's another post from the "Sequences" that I was thinking of instead.
With such skepticism, how are you even able to write anything, or understand the replies? Or do anything at all?
Also, your argument (including what you have said in the comments) is something like this:
Every argument is based on premises. There may be additional arguments for the premises, but those are arguments will themselves have premises. Therefore either 1) you have an infinite regress of premises; or 2) you have premises that you do not have arguments for; or 3) your arguments are circular.
Assuming (as you seem to) that we do not have an infinite regress of premises, that means either that some premises do not have arguments for them, or that the arguments a...
Memories can be collapsed under percepts.
In answer to your broader question - yup: you've hit upon epistemic nihilism, and there is no real way around it. Reason is Dead, and we have killed it. Despair.
...Or, just shrug and decide that you are probably right but you can't prove it. There's plenty of academic philosophy addressing this (See: Problem of Criterion) and Lesswrong covers it fairly extensively as well.
http://lesswrong.com/lw/t9/no_license_to_be_human/ and related posts.
http://lesswrong.com/lw/iza/no_universally_compelling_arguments_in_math_or/
R...
gjm has mentioned most of what I think is relevant to the discussion. However, see also the discussion on Boltzmann brains.
Obviously, if you say you are absolutely certain that everything we think is either false or unknown, including your own certainty of this, no one will ever be able to "prove" anything to you, since you just said you would not admit any premise that might be used in such a proof.
But in the first place, such a certainty is not useful for living, and you do not use it, but rather assume that many things are true, and in the second place, this is not really relevant to Less Wrong, since someone with this certainty already supposes that he knows that he can never be less wrong, and therefore will not try.
Assume they're approximately true because if you don't you won't be able to function. If you notice flaws, by all means fix them, but you're not going to be able to prove modus ponens without using modus ponens.
I would agree if you can't trust your reasoning then you are in a bad spot. Even Descartes 'Cogito ergo sum' doesn't get you anywhere if you think the 'therefore' is using reasoning. Even that small assumption won't get you too far but I would start with him.
Standard methods of inferring knowledge about the world are based off premises that I don’t know the justifications for.
How do you come to that conclusion?
Any introduction or reader on contemporary epistemology that you'd find on amazon would address these three points.
You can think of what the points mean in the technical sense and try not to read anything more into them.
1) You sense something, your brain state is conditional on atleast some part of the universe. Do not make assumtions on whether it's a "fair" or "true" representation. At the most extreme you could have a single bit of information and for example no insight on how that bit is generated (ie by default and from epistemoligcal first grounds our behaviour is opaque).
2) We move from one computation state to another based on non-vanishingl...
Also, I've asked my philosophy professor pretty much the same question and he referred me to Hegel. I'm probably terribly misinterpreting what he said but here it is: the awareness of the imposs...
“One has knowledge of one’s own percepts.” Percepts are often given epistemic privileges, meaning that they need no justification to be known, but I see no justification for giving them epistemic privileges. It seems like the dark side of epistemology to me.
Why? I realize that Yudkowsky isn't the most coherent writer in the universe, but how the heck did you get from here to there?
A simple qualia-based argument against skepticism (i.e. percepts are simply there and can't be argued with) is problematic- even if you conceded direct knowledge of percepts, ...
Standard methods of inferring knowledge about the world are based off premises that I don’t know the justifications for. Any justification (or a link to an article or book with one) for why these premises are true or should be assumed to be true would be appreciated.
Here are the premises:
“One has knowledge of one’s own percepts.” Percepts are often given epistemic privileges, meaning that they need no justification to be known, but I see no justification for giving them epistemic privileges. It seems like the dark side of epistemology to me.
“One’s reasoning is trustworthy.” If one’s reasoning is untrustworthy, then one’s evaluation of the trustworthiness of one’s reasoning can’t be trusted, so I don’t see how one could determine if one’s reasoning is correct. Why should one even consider one’s reasoning is correct to begin with? It seems like privileging the hypothesis, as there are many different ways one’s mind could work, and presumably only a very small proportion of possible minds would be remotely valid reasoners.
“One’s memories are true.” Though one’s memories of how the world works gives a consistent explanation of why one is perceiving one’s current percepts, a perhaps simpler explanation is that the percepts one are currently experiencing are the only percepts one has ever experienced, and one’s memories are false. This hypothesis is still simple, as one only needs to have a very small number of memories, as one can only think of a small number of memories at any one time, and the memory of having other memories could be false as well.