Thoughts on Epistemology Part of my response to MU...
So there's no confusion, let me suggest that there are sensory statements (like Moore's claims to knowledge about having hands in response to the skeptic) that lie outside of epistemological language-games. However, much of this is driven by context, but not all of it, since one can use statements like "I know..." in context, and still use the words incorrectly (Moore's case). The point is that we need to be able to distinguish between the two, viz., those that are understood in terms of justification, and those that fall outside any need for justification. Wittgenstein makes this distinction in On Certainty again and again. Thus, the question arises, what separates the kind of sensory statements that are perfectly normal in terms of being justified, from those that need no justification (again Moore's statements/propositions)? The answer to this question lies in another question, "Does it make sense to doubt the claim?" One must not forget the language-game of doubting when trying to understand the difference between these two kinds of sensory claims.
Moore is standing before an audience raising his hand and makes the statement that this is a hand, i.e., that he knows it's a hand. But what would a doubt here look like? Did Moore double-check to make sure those were his hands? Moreover, what would making sure look like? We can juxtapose this with a statement that does make sense to doubt, and Wittgenstein gives just such an example in the following: "And if he says he knows it, that can only signify to me that he has been able to make sure, and hence that his arms are e.g. not still covered in bandages, etc. etc. My believing the trustworthy man stems from my admitting that it is possible for him to make sure (OC 23)." In this case one may awaken from an operation in which it was in doubt about whether the infection was so severe that one might lose a hand. I wake up, my hand is still bandaged and numb from the operation, so I'm still in doubt about whether I have a hand, i.e., I don't know that I have my left hand. The bandages are removed, and I see (sensory observation) that my hand was not removed during the operation. I now know, based on what? How did I make sure? What is the justification? Lo and behold, I still have a hand!
Science also makes use of sensory observations in terms of what they claim to know. They observe experiments, and write down their observations. They make discoveries of new planets based on what they SAW through their telescopes. How do you know there is a planet in such-and-such a place? I observed it, and you can observe it too, look and see. These are not subjective observations. They can be objectively verified. The same is true in my orange juice is sweet example. How do I know the orange juice is sweet? I tasted it. Here, you can taste it too. Ahh, yes it's sweet, or no, it's not sweet. Obviously if others taste the orange juice and it's not sweet, then the person wasn't justified in making the claim that it was sweet. Just like scientists can verify a claim that such-and-such is planet, i.e., others can observe (see) whether the claim is true (objective verification) - making sure. Many claims are justified in just this way.
It would be ludicrous to claim that sensory experiences are not acceptable methods of justification. Obviously this doesn't mean that we accept every sensory observation, but generally it's true that we can rely on sensory observations as a perfectly acceptable method of knowledge.