What are examples of non-physicalist approaches to acquiring knowledge?

Question

As a follow-up to my previous question Is non-physicalism reasonable?, I would like to know about non-physicalist ways of acquiring knowledge that philosophers have considered. What sorts of knowledge can be acquired through (partially) non-physicalist means, according to alternative views that reject the thesis of physicalism (i.e., that everything is physical)? Can anything at all be known about the (purported) non-physical aspects of reality, and if so, how?

Answer 1

You say:

The physicalist claim everything is physical.

This is the claim of an eliminative materlialist, not all physicalists. I'm not sure that all forms of physicalism are so radical. There's nothing wrong with conceding thoughts, mental states, and fictions are things which are not physical, as long as one understands that they can be understood to at least partially reduce to the physical. Property dualism is an alternative to eliminative materialism. From WP:

Property dualism describes a category of positions in the philosophy of mind which hold that, although the world is composed of just one kind of substance—the physical kind—there exist two distinct kinds of properties: physical properties and mental properties. In other words, it is the view that at least some non-physical, mental properties (such as thoughts, imagination and memories) exist in, or naturally supervene upon, certain physical substances (namely brains).

A mathematical proof is a non-physical approach to the acquisition of knowledge. Given premises, one infers using language, a conclusion. If the conclusion is a truth-apt proposition, then associating it's truth value with the proposition satisfies the rough outline of justifying and judging required to have a true claim. For instance, if one moves from the normal form of a quadratic equation to the solution for the roots of the equation (the quadratic formula), one has produced knowledge which is fundamentally not empirical, but rational. These sorts of rational conclusions are not physical.

Contrast that to measuring the dimensions of the Great Pyrmaid of Giza. In no possible world is the height of Giza a function of cultural forces, other propositions, claims divorced from physical reality. The height of that specific pyramid is empirical and knowable only through the presumptions held by physicalist doctrine and measurement theory. It is an empirical fact that the Great Pyramid has mass and extension, that the Pyramid exists over an interval of time and is subject to entropy, and will lend itself to other physical claims. Claims about the physical description of the Great Pyramid are generally physical claims.

Thus, just because experience and mental states have no physical existence, doesn't mean that they are not real, just not physically real. Therefore knowledge (which is generally construed as a collection of propositions) is generally, but not absolutely sortable into rational and empirical sorts, and neither are divorced from the other as the mind cannot be purely rational or empirical, but integrates the two sorts of experience. All rational methods of acquiring knowledge are generally non-physical in this sense.

Answer 2

Neither evidence, nor knowledge, can be "physical". It is a logic error to think otherwise.

Epistemology, the philosophic principles of ho one gains knowledge, is PRIOR to theories about what that data, or knowledge reveals. Physicalism is a theory about the universe, it is derivative from epistemology, evidence and knowledge. Epistemology, the data it then uses, and the knowledge it provides, is therefore all non-physical.

It is a challenge for any theory about our universe to explain or accommodate the circumstances that lead to its adoption, and physicalism is generally able to explain and accommodate physically based evidence and experiments. Physicalism struggles more with information, and relationships, as its heritage as a philosophy is closely associated with materialism, and neither of these are material. But if one realizes that PHYSICS requires information and relationships, and physics is therefore not monist, but is a fusion of materialism and abstractions, and therefore physicalISM cannot be a monist ontology, then physicalism is also able to accommodate both information and relationships.

What physicalism struggles to accommodate, is the justification of epistemology, the concept of knowledge, the concept of evidence, and the primary way we collect evidence which is by first person qualia. Plus reasoning, as other posters have pointed out.

It is easy to test non-physical theories. Lets take some examples. If we combine say the theory of Godly authorship of some divine literature, with postulating a God being Omniscient, then if that divine literature has some errors in it, such as describing atmosphere and life on the moon, or cosmology as a flat-earth-dome-sky snowglobe model, or miscalculates the value of Pi, or the number of fractions that add up to a full inheritance, then one can reasonably conclude that the non-physical hypothesis was false. There is nothing special about non-physicalist hypotheses that make them any less testable than physicalist ones.

Answer 3

Most knowledge you obtain is obtained through non-physical means. When your teacher tells you that gravity acts to accelerate objects near the Earth's surface at ~10m/s, you don't obtain that knowledge through physicalist means... even if the origin of that knowledge rests in physicalist principles.

The reason I mention this is because it should make more obvious a more reasonable answer to your question. Namely, if a deity existed, and were capable of interacting with the physical universe, and chose to do so, and chose to impart knowledge while doing so... that knowledge would be wholly non-physicalist. In particular, such a deity might use this method to communicate knowledge of things which are themselves not physical.

You've probably noted that this is the basis for most religions.

Now, however, a problem appears; namely, how does one trust such revelations? Ultimately, as with last thursdayism, a perfect hoax might be impossible to detect. Still, some useful metrics are the extent to which such non-physicalist knowledge seems to be consistent with what we can observe, as well as whether such knowledge gives predictions which can be verified.

Answer 4

Knowledge is a non-physical concept. Knowledge has no physical properties whatsoever. All approaches to acquiring knowledge are non-physicalistic.

Physicalist knowledge is an oxymoron.