Tuesday, September 23, 2008

The Nature of Evidence

I'd like to elaborate on a point I made in my last post (the topic was consciousness), as it will help explain my views on science in general and consciousness in particular. I wrote:

"If there were any evidence that consciousness (or anything else) were so unique that it could not be explained objectively, that evidence could not be shared. For, if it could be shared, then it would be objectively determinable. Therefore, from a scientific point of view—that is, from a point of view which regards facts as sharable and repeatable through well-documented experiments—there can never be any evidence that consciousness (or anything else) is beyond the hopes of a scientific explanation."

One might ask, Why can't we have evidence that is not scientific? Can't we have evidence based on our own intuition or personal experience? Why must all evidence be sharable and repeatable?

I acknowledge the fact that we are often in the position of having to make decisions based on evidence which we cannot share with other people.
However, the point is not that we must always share our experiences, or that we must always be in a position to share them. Rather, the point is that, when we regard something as evidence, we are regarding it as something which can be shared and repeated. If it cannot be shared and repeated, it is not evidence.

Ah, you say, now you're just stacking the deck in science's favor. You're conveniently defining "evidence" to only include stuff that science can deal with, and ignoring all the other stuff that makes life so special.

No, I don't think that's the case. Rather, the point is this: If you want to put something on the table--if you want to organize our discourse and politics around some fact or idea--then you need to be able to share it or reproduce it for us, or share/reproduce some evidence for it. If you cannot do that, then you are drawing our attention to nothing. (This happens a lot, unfortunately).

Why should we organize our beliefs and policies around something we cannot observe and measure? It makes us vulnerable and inefficient. Civilization requires principles of evidence to protect it from stupidity. (Imagine a legal system without evidentiary rules. Imagine civilization without law. See my point?)

Sometimes our need to make decisions/judgments forces us to suspend our principles slightly. Thus, we may take people at their word without requiring substantial evidence. This is also necessary for civilization: we must trust each other when circumstances prevent us from collecting enough evidence to make an informed decision. But civil society also requires that we do this as little as possible, and that we have a good reason for doing it when we do. (This is, incidentally, why we have such things as reputations. Reputations help us make more intelligent risk assessments on issues of trust.)

The key point here, however, is that even when we take people on their word (or on their reputation), we are not defying science. We are not adopting some other standard of evidence. On the contrary, we are only trusting that people are going to act responsibly with respect to their own experiences. This means we expect people to treat their own experiences from as scientific a perspective as possible, as practical considerations allow. (The fact that people are not always so responsible is beside the point. We have ways of dealing with irresponsibility, some more effective and desirable than others.)

There remains a desire to think of some evidence as purely "personal." Isn't intuition (or perhaps spiritual revelation) an alternative to scientific ways of thinking?, you insist.

As I see it, the answer is no. The idea that there could be some other, non-scientific approach to evidence is just confused wishful thinking which arises when people fail to recognize what counts as "personal evidence."

There is no justification for claiming that some unrepeatable, unsharable private experience counts as evidence of some arbitrary fact. E.g., "I saw something strange in the sky, therefore aliens from Mars are attacking." Or, "I had a dream about my grandfather, therefore he is looking after me from beyond the grave." These ways of thinking occur often enough, but they are irrational. They might make people feel nice and important, but they are not based on an alternative form of evidence. Rather, they are based on a rejection of all standards of evidence.

I am not saying that people should ignore their intuitions and dreams. I think it is a good idea to acknowledge your intuitions and dreams and let them guide you in some ways. But we should not mistake them for evidence. Intuitions and dreams are perfectly capable of misguiding us. Again, this is why we have standards of evidence.

Our subjective experiences are sometimes hard to define, and we don't always count them as evidence of anything. For our experiences to count as evidence, we require them to be in some way repeatable and sharable. If we don't, then we are not being rational, and instead basing our beliefs on whim and fancy.

I expect some of you to object here, and say, Feelings like love and anger are easy to define and recognize, and yet cannot ever be shared.

Yet, we can share our feelings. Imagine a life where you couldn't share your feelings with anyone. It would be miserable.

We can perform any number of outward signs to demonstrate our feelings. Some people try to fake their feelings sometimes, but it is pretty easy to spot a bad actor. The best actors are the ones who don't fake it.

Okay, you ask, maybe we can share our feelings, but what about thoughts?
Certainly, evidence for something like abstract thought cannot be shared, right?

No amount of body language will tell you that I'm thinking about how many apples I found in the garbage can in my sister's bedroom on Halloween in 1989? What about the language I am using to type this sentence?

Evidence for abstract thought is shared all the time. You're reading evidence of it right now.

So, as it turns out, there isn't anything about our "personal evidence" that is forever beyond sharability or repeatability. No experience is so private that it cannot, at least in theory, be shared and reproduced in some way.


This view is necessary, because no evidence can be had for the contrary view. You cannot provide evidence which demonstrates that something exists for which there is no evidence. It would be a contradiction.

Our "inner lives" aren't as private as we might like to think. I think this fact will become much more obvious in the near future, as we come to better understand how the brain works. We're already developing technologies which allow us to practically read (and write to) people's minds. We may be approaching the end of the time when people could think of their own thoughts as their own, personal business.