Whaddaya Know?

A traditional religious Jew claims to "know" that the Torah is the revealed word of the one God.

A traditional religious Catholic claims to "know" that the Eucharist is really, truly and objectively the body and blood of Christ.

A traditional religious Muslim claims to "know" that angels exist as incorporeal beings, including the three main angels, Jibril, Israfil, and Azrail.

A religious Mormon claims to "know" that Jesus Christ appeared to Native Americans in North America after his crucifixion at Golgotha.

None of these things constitute knowledge. In fact, none of them is true, but that's a subject for future posts. This post is about the nature of knowledge.

I started to write a short post on what it means so say that "I know" or that "we know" something. But it turned into a long post. So I've put it on a separate web page here. The capsule summary is:

• We know nothing about the real world with certainty. (We can know mathematical truths with certainty, but only because they are truths about objects that we have ourselves defined, and whose properties we have specified. Such truths - e.g. that there are an infinitude of prime numbers - are not about objects in the physical world.)
• The scientific method is the best - indeed, really the only - objective way that we have developed to gain knowledge about the real world.
• There is no subjective way.
• The scientific method enables us to disprove conclusively hypotheses about the nature of reality. It does not enable us to prove them, but it does allow us to know with very high probability what is true.
• More importantly, the scientific method enables us to put constraints around what might possibly be true. Thus, if you have a new theory of gravity, it must conform to all the accurate observations made to date about how gravity behaves.
• Useful hypotheses make unambiguous predictions that can be tested.

There are other ways people use for "knowing". They include:

• Introspection. This may be a way of knowing about your own inner state (although it turns out to be a very poor way; see this classic paper on social psychology.) Absent further advances in neurobiology, it may be the only way. But it is not a valid way to gain knowledge about the external world.
• Authority. This simply reduces the question to one of how the authority claims knowledge, and how accurately you understand and represent the authority.
• Revelation. This is, I contend, self-deception at best, and psychosis at worst. After all, people claim certain knowledge through revelation of many things such as different religious "truths" that are inconsistent with one another. At most one of them could be correct. In any case, if knowledge obtained via revelation can be tested, then you are actually using the scientific method to know. If it cannot be tested, then it is not knowledge.

For details I refer you to the long post. Let's review the four pieces of claimed knowledge that I cited at the beginning of this post.

The claim that the Torah is the revealed word of the one God is a claim based on authority - rabbinical authority in this case. There is no direct evidence for this claim. Indeed, there are so many internal contradictions in the Torah (order of creation in Genesis 1 vs. Genesis 2, number of animals taken on Noah's Ark in Genesis 6:19 vs. Genesis 7:2, etc.) that there could not be such evidence unless God made some mistakes.

The claim that the Eucharist is the body and blood of Christ is based on papal authority, which is based on papal interpretations of the gospels. In so far as it has been tested (by chemical analysis of the wafer and wine) it is, of course, false. If the claim is that The Eucharist is the body and blood of Christ in some other-than-physical way (see this article for a discussion) then it's not testable, and perhaps not meaningful.

The claim that angels, and those three angels in particular, exist as incorporeal beings is a claim to the authority of the Qur'an, which in turn is a claim via revelation of the Qur'an to Mohammed. It's not clear that it's testable.

The claim that Jesus visited North America after his crucifixion is based on revelation to Joseph Smith. To the extent that it can be tested via archaeological evidence, none has been found. It's not clear that it's testable.

So none of these constitute knowledge as I use the term.

I'll end with a quote from Stephen Jay Gould:

In science, "fact" can only mean "confirmed to such a degree that it would be perverse to withhold provisional assent." I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.