Pray for them. Just kidding, though perhaps a prayer would not be uncalled for! I wonder if your friend is an extreme skeptic when it comes to empirical experience. Perhaps he is akin to Peter Unger in his book Ignorance, in which he seeks to undermine our confidence in our claims to know about ourselves and the world. Plato seemed to adopt a position not completely unlike your friend: he appers to have held that we may be more certain of the things of reason (mathematics, knowledge of the forms) than we can about the reliability of our senses. It is easy to have some sympathy with such an outlook: I am, for example, more convinced that 2+2=4 than I am convinced that I am not merely dreaming about the website AskPhilosophers. But your friend is in an usual position. Most of the philosophers who today defend the evidential role of religious (or spiritual) experience such as Richard Swinburne, William Alston, Jerome Gellman, Caroline Franks, K.M. Kwam, etc, argue for the reliability of such experiences by analogy with the reliability of ordinary perceptual experience. In other words, they treat what you are callling empirical evidence as veridical and sound and then, while conceding that religious experiences are not as uniform and are more varied, etc, they then argue for taking religious experience seriously. In this line of reasoning, though, none of them (to my knowledge) think that "spiritual experience is the most reliable basis for establishing truth" versus "empirical evidence."
If Mediums did get "results" then it would be rational to go to them for advice i.e. not a waste of time!
So I think the thing to focus on is the results, and ask the question, are the amazing pronouncements just coincidences and/or wise vague sayings? There's no shortcut to answering this--it is an empirical question. Remembering of course, that Mediums, TV and authors don't always report reliably.
This may not be much help but I would say "to some extent." There can be no doubt that judgments based on introspection are sometimes wrong. I have often had the experience of thinking that I did something with one motivation only to realize later that there was another at work as well. Also, our introspective judgments are often self serving. We need to approach them with a degree of skepticism.
The veracity of our inner soundings also depends on the concepts that we are looking at ourselves through. It makes all the difference in the world whether I examione myself through a Freudian, Marxist, or purely phsycalistic lens. Whether looking out or rolling our eyes balls in looking in - what we see is deeply impacted by the ideas that we are peering through.
You are asking whether it is true that T=K (knowledge and truth are the same). From your asking this, I conclude that you don't know whether T=K. If truth and knowledge were the same, then lack of knowledge would be lack of truth. So, assuming T=K is true, we derive the conclusion that T=K is false.
Better then to suppose that knowledge and truth are not the same.
And of course they aren't. Something may be true and yet not be known by many or not be known by anyone at all. For example, take the following two sentences: "with optimal play, white can always win in chess" and "it is not the case that, with optimal play, white can always win in chess". One of these sentences is certainly true; but no one yet knows which one it is. (Or, if anyone does now, they haven't told me, so I don't know which is true.)
There is certainly something of Hume's reasoning in your question (see the end of section v of the first Enquiry). And, this way of thinking about knowledge becomes a basic definition of knowledge in pragmatism (Pierce, James et al). However, it is inappropriate in Kant. We must take what you term the categorical difference between things-in-themselves and appearances seriously. Appearances are the only domain of knowledge. This is not because appearances are what we are directly acquainted with, while things-in-themselves are in some way hidden. If that were the case, as you say, there would be good reason to think that the former would have to be correlated with the latter, and that through this correlation, the latter could come to be known. Rather, we should say that the thing-in-itself is such as to not be a possible object of knowledge. In other words, whatever forms of knowledge would be necessary to know a thing-in-itself (even talking about a 'form of knowledge' here is probably already going too far), that form of knowledge is impossible for any human mind.
hm. why can't we methodically critique the possibility of knowledge in various domains w/o ever explicitly addressing the question of whether we can 'know' that knowledge (in general) is impossible? or, is it really self-contradictory (a paradox) to claim that all knowledge is impossible, even this -- for when one denies 'knowledge' one typically replaces it with something less prestigious (like belief, maybe) -- and so one can coherently say I believe that no knowledge is possible (and that belief is the most we can get) .....?
Wow, fantastic email -- getting at the heart of some major philosophical ideas and movements. Empiricists tend to stress the role of perception/experience in producing knowledge, while rationalists tend to promoe the role of reason, often arguing on the basis of such considerations as those you mention. A couple of quick thoughts about the specifics of your message. Your example of a problematic perception (spinning cube looks like sphere) doesn't quite/fully show that perception is problematic, partly because some other perception is relevant to getting at the truth, ie seeing the cube not spinning. The rationalist might say that reason is needed to process these otherwise conflicting perceptions, but even if this so, it does seem that perception is playing a key role in generating our knowledge of the world (that a cube exists, and that, when spun, it looks spherical) -- so what you've raised is a kind of problem for perception, but not one which obviously (to me anyway) undermines the importance of eprception in generation knowledge. Second, you mention the 'gap' between reality and minds -- and probably need to say more there. Even if everything we come to know about the empirical world were ultimately, in some way, derived from perception, it remains possible that perception is 'veridical' -- gives us true information about the world -- so the sheer fact that our access is mediated via perception does not entail that perception isn't veridical, or even direct .... This doesn't fully answer your excellent question -- how do we know we have knowledge not just perception? but aims to suggest that perception may well play important roles in generating knowledge despite the two kinds of worries you raise ....
hope that helps!
Just a minor addition to Mitch Green's astute observations: Some defenders of the coherence of omniscience (Richard Swinburne, for example), hold that omniscience does not include the knowledge of future free acts. Swinburne and R.M. Adams and others do so on the grounds that there is no truth or falsehood now about what a future free agent will do. Aristotle held this as well (or at least most commentators think so!). If this viewpoint is correct, "omniscience" would mean something like all that it is possible to know or all that can be known. If future free action is not knowable in principle then any being, even an omniscient being, would not know something and thus would know what it is like to be ignorant. For an excellent book on omniscience and other divine attributes, check out Richard Swinburne's The Coherence of Theism.
Professor Green rightly notes that some philosophers have worried about the limits of knowledge that might be in play if a being is incorporeal. And I must agree that Wings of Desire is a most excellent film. I would only add that problems arise for theism only depending upon your view of emotions, sensations, and perception. If you believe that these are only and exclusively physical processes and states (that is, if you believe it is a necessary truth that such processes cannot be nonphysical or be entertained by an incorporeal being ), then God (if God exists) does not have such processes and states, but significant numbers of philosophers believe that either such processes are not themselve exhuastively physical with us or other animals (John Foster, Howard Robinson) or they maintain that these processes in us are physical but only contingently so. Thus, Peter VanInwagen accepts a materialist view of humans and our cognitive powers, but he is not a materialist when it comes to God and divine cognitive power.
Much of what we know is based on the evidence of testimony, rather than the evidence of our senses. Consider your knowledge of your birthday. Your evidence that you were born on a particular date is based on information from your parents, your birth certificate, and other testimonial evidence. You were there, of course, and you were sensing. But the sensory information you had at the time did not count as evidence. Your knowledge of your birth is a bit of empirical knowledge, as are other items of historical knowledge. Indeed, a great percentage of your beliefs are based on the testimony of others.
Your excellent question about whether testimony is “subsumed by empirical knowledge” might be understood as the question of whether testimonial knowledge can be reduced to some more basic kind of empirical knowledge, such as sensory-based knowledge. This is a controversial issue in the epistemology of testimony. Some beliefs that are justified by testimony can be independently checked by first-person observation. But your knowledge of your birthday can’t be so checked, and you can’t observe whether Caesar was killed on the ides of March. Some epistemologists hold that your justification based on testimony must be supported by other beliefs about the reliability of the source of testimony, and that such justifying beliefs must ultimately be supported by first-person sensory evidence. You might have supporting sensory justification for the reliability of the reports of your parents, for example, since you may have been able to independently verify their testimony on many occasions, and you conclude that they are reliable testifiers. Others hold that testimony is a basic form of testimony that doesn’t require sensory justification, though, like sensory evidence, it is fallible and subject to correction. These issues are addressed in a very good anthology edited by Jennifer Lackey and Ernst Sosa, The Epistemology of Testimony.