Evidence

This entry was posted on Tuesday, February 27th, 2007 at 8:57 pm and is filed under Philosophy. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

18 Responses to “Evidence”

Bradford Says:
February 28th, 2007 at 12:02 am
The importance of the question is evident when one considers that we all have access to the same data and two individuals looking at the same set of facts can come to different conclusions. We would probably save ourselves time and energy by asking those of opposing views one question. What would convince you that x is plausible? The answer to that would determine whether follows ups are worthwhile.

Comment by Bradford — February 28, 2007 @ 12:02 am

Mesk Says:
February 28th, 2007 at 12:21 am
Bradford,

Although it's true in theory that we all have access to the relevant data, that isn't the case in practice. The evidence relevant to evolutionary theory is largely tucked away in the academic literature, which is (a) difficult to access without institutional subscriptions, and (b) exceptionally difficult for the layperson to penetrate, given the jargon and assumed background knowledge that permeates every scientific paper. Even for those who do have the means and the knowledge to explore the scientific literature, the time required to absorb all of the relevant data is simply unavailable to most of us (well, actually to all of us – it's actually physically impossible to read all of the literature published in biology, even if reading papers was all you did all day).

So most individuals on both sides of this debate rely instead largely on the mainstream media, popular science publications, and scientific blogs to build their knowledge. All of these sources are rife with misleading and incomplete information, and all project their own opinions while presenting the data (as does the scientific literature itself, in fact). Since we all tend to favour sources that validate our own opinions, confirmation bias is rampant, and demonisation of the opposition near-universal.

I'm actually starting to reach the pessimistic conclusion that none of us have the requisite knowledge to have an informed opinion about anything.

Comment by Mesk — February 28, 2007 @ 12:21 am

inunison Says:
February 28th, 2007 at 1:48 am
Mike,

Excellent question. That is why science alone cannot give us complete picture of reality. We have to put data in context of a world-view in order to make sense of our world.

Mesk is right when saying:

Since we all tend to favour sources that validate our own opinions, confirmation bias is rampant, and demonisation of the opposition near-universal.

However, confirmation bias is just about inevitable and it does not have to be a bad thing providing we are prepared to argue our conclusions openly and in return listen to opposition and if necessary redefine our own position .

Comment by inunison — February 28, 2007 @ 1:48 am

Douglas Says:
February 28th, 2007 at 4:22 am
What is truth?

Comment by Douglas — February 28, 2007 @ 4:22 am

MikeGene Says:
February 28th, 2007 at 5:06 am
Hi inunison,

You write:

However, confirmation bias is just about inevitable and it does not have to be a bad thing providing we are prepared to argue our conclusions openly and in return listen to opposition and if necessary redefine our own position .

Hold that thought. What you have just described is at the heart of the Design Matrix.

Comment by MikeGene — February 28, 2007 @ 5:06 am

bipod Says:
February 28th, 2007 at 1:18 pm
I'm actually starting to reach the pessimistic conclusion that none of us have the requisite knowledge to have an informed opinion about anything.

Mesk, I totally understand your reasoning here, and I take a similar position, but rather than "informed opinion" I'd use "confident opinion" – I think we can have informed opinions but should hold them within the context which you describe – a context that should ultimately drive us to be non-dogmatic and open-minded.

Comment by bipod — February 28, 2007 @ 1:18 pm

BenK Says:
February 28th, 2007 at 3:24 pm
Heheh.

I really like the Bayesian approach to philosophy of science which goes something like:

The probability of a theory given an observation equals:

The probability of that observation assuming the theory is correct, times the prior probability of the theory being correct, all divided by: the probability of the observation given all of the theories currently considered by the scholarly community.

Or:

P(T|O) = {P(O|T) x P(T)} / {P(O|T) x P(T) + P(O|~T) x P(~T)}

Hard to get your head around in the first place, but actually quite elegant. Simply put, it has these implications:

1. The more a theory predicts an observation, the more the observation counts as evidence for that theory.

2. The less other theories predict an observation, the more that observation counts as evidence for the theory being considered.

3. 'Prior Probabilities' are vital. If a theory is generally considered nonsense, even a really good piece of evidence won't be seen as a confirmation of that theory. Conversely, if a theory is considered capital T Truth, then even an obstinate problem that other theories can more elegantly solve won't necessarily seen as a falsification of the theory.

This means that 'evidence' has a powerful social dimension; the meaning of a given observation is determined by the current state of debate within the scholarly community.

Comment by BenK — February 28, 2007 @ 3:24 pm

Deuce Says:
February 28th, 2007 at 3:53 pm
Hi Mesk,

I'm actually starting to reach the pessimistic conclusion that none of us have the requisite knowledge to have an informed opinion about anything.

Hi, Mesk, you're reaching a very similar place as Descartes. He concluded that the only things he could be sure of were the existence of appearances (since even if all your appearances of the outside world are illusions or mistaken, the appearances themselves must still exist), and thus the existence of himself having the appearances ("I think, therefore I am"). I agree with him on that, and with bipod re: confident opinions on most everything else.

Comment by Deuce — February 28, 2007 @ 3:53 pm

great_ape Says:
February 28th, 2007 at 8:05 pm
"…times the prior probability of the theory being correct" == BenK

It's the above fragment of the Bayesian approach that makes it unpalatable for many scientists. There are some limited circumstances where one might have approximate knowledge of the probability distribution for the theory itself (e.g. the probability that the theory 'George is HIV positive' may be approximately the frequency of HIV in the relevant population for George) but in most cases the priors are pulled out of the researcher's you-know-what. Alternatively, they are considered uniformly probable, in which case the Bayesian approach is effectively the same as using Maximum Likelihood, which most folks are comfortable with b/c there are no priors.

Comment by great_ape — February 28, 2007 @ 8:05 pm

great_ape Says:
February 28th, 2007 at 8:07 pm
Mesk:

I'm actually starting to reach the pessimistic conclusion that none of us have the requisite knowledge to have an informed opinion about anything.

Would you consider this pessimistic conclusion an informed opinion?

Comment by great_ape — February 28, 2007 @ 8:07 pm

Joy Says:
February 28th, 2007 at 8:24 pm
Would you consider this pessimistic conclusion an informed opinion?

Comment by Joy — February 28, 2007 @ 8:24 pm

Mesk Says:
February 28th, 2007 at 9:11 pm
Hmmm… I quite like bipod's terminology – in which case it would be an informed opinion, but not a confident one.

For the record, my pessimism was somewhat exaggerated, but I do feel that most people express undue confidence in the probability of their current opinions being ultimately correct, and of the opinions of their opponents being fundamentally wrong. I also think the emphasis on an "advocacy" style of debate increases this effect, by forcing people to polarise their opinions. The reason I like TT is that most people here are closer to the middle than on any other evolution/creationism/ID forum I've ever visited, making it (occasionally) possible for constructive dialogue to take place.

Comment by Mesk — February 28, 2007 @ 9:11 pm

BenK Says:
February 28th, 2007 at 9:26 pm
Oh, I take the bayesian account of Philosophy of Science as descriptive rather than normative. I wouldn't expect the scientist to sit down and run through the equation everytime they made an observation. But I do think it's an eloquent of how science (in fact, I would say scholarship, even belief in general) actually works, but for the individal and for the scholarly community; I do have my own 'prior probabilities' for different ideas (ie, I grade them from almost certainly true through probably true, possible, probably untrue, and almost certainly untrue), and the impact of observations on my beliefs is in large part determined by these prior probabilities.

That's why the old 'Extreme Claims require Extreme Evidence' chestnut is true in a subjective sense, but useless as an argument for or against a position. Take the claim of a miracle, for instance. The ardent materialist needs absolutely undeniable evidence for a miracle to a degree which he would never demand for anything else; a single miracle would require him to reevaluate his entire worldview (i.e. 'miracle' has a tiny prior probability). Meanwhile for a Christian, belief in a miracle would require solid evidence (as miracles are rare), but nothing like the evidence demanded by the materialist, because it sits comfortably within his existing framework of belief (i.e. has a higher prior probability).

Which is to say that 'Extreme claim' is in the eye of the beholder, as is 'Extreme evidence'. Ultimately I think a grand mistake so many people make is to believe that there is some objective, 'netural' position from which we should all attempt to evaluate observations as evidence for and against positions. There is no such objective, neutral position. Everything we evaluate, we evaluate from our own network of beliefs and assumptions, and there is nothing 'neutral', or 'objective' about that.

Comment by BenK — February 28, 2007 @ 9:26 pm

BenK Says:
February 28th, 2007 at 11:26 pm
typo correction, that should have read:

"…I do think it's an eloquent account of how science (in fact, I would say scholarship, even belief in general) actually works, both for the individal and for the scholarly community;…"

Comment by BenK — February 28, 2007 @ 11:26 pm

great_ape Says:
March 1st, 2007 at 9:11 pm
""¦I do think it's an eloquent account of how science (in fact, I would say scholarship, even belief in general) actually works, both for the individal and for the scholarly community;"¦" BenK

Agreed. The Bayesian approach seems much more in tune with our basic intuitions about how evidence for a theory or group of theories is weighed. As a formal statistical methodology, though, it is only somewhat recently (~6-10 yrs?) that it's becoming mainstream–at least in my field. So as I was going through school, I got to hear a lot of the older profs express their various reservations about it. The Bayesian vs. Likelihood debate was always interesting to me b/c it's one of the most clear-cut cases where people's philosophy (in this case, there philosophical views on statistics) have an easily observed impact on how they conduct and judge practical research.

Comment by great_ape — March 1, 2007 @ 9:11 pm

BenK Says:
March 1st, 2007 at 9:16 pm
I did a 3rd year unit on the current state of the Philosophy of Science for my BA only 2 years ago; I think I missed that debate. Sounds very interesting though, I think I'll Google it now.

Comment by BenK — March 1, 2007 @ 9:16 pm

Zachriel Says:
March 2nd, 2007 at 4:43 pm
Mesk

The evidence relevant to evolutionary theory is largely tucked away in the academic literature, which is (a) difficult to access without institutional subscriptions, and (b) exceptionally difficult for the layperson to penetrate, given the jargon and assumed background knowledge that permeates every scientific paper.

How do we know what we know?

Scientific evidence consists of observations that can support or counter a specific scientific hypothesis.

Many aspects of science can be easily confirmed. We can repeat the experiments of Galileo, build a telescope and see the phases of Venus. Like Faraday, we can make an electric motor to demonstrate the relationship between electricity and magnetism. We can make a microscope, just as Leeuwenhoek did, and rediscover tiny animacules swimming in a single drop of water. We can see the spectrum of the Sun by using a prism, just as Newton did.

Or we can take a hike, examine the geologic column, and verify the maps of geologists, such as those of William Smith "” perhaps even finding a few common fossils. And after having reasonably verified these observations, we can have confidence in the findings of geology, paleontology, and the succession of fossils.

It is the repeatability of scientific observations that allows us to have confidence in our conclusions.

Comment by Zachriel — March 2, 2007 @ 4:43 pm

Zachriel Says:
March 2nd, 2007 at 4:50 pm
When is an appeal to authority valid?

An appeal to authority is valid when
* The cited authority has sufficient expertise.
* The authority is making a statement within their area of expertise.
* The area of expertise is a valid field of study.
* There is adequate agreement among authorities in the field.
* There is no evidence of undue bias.

The proper argument against a valid appeal to authority is to the evidence. However, a reasonable layperson would be very cautious in challenging a brain surgeon on the proper techniques in brain surgery.

Mesk

So most individuals on both sides of this debate rely instead largely on the mainstream media, popular science publications, and scientific blogs to build their knowledge.

Mainstream media is considered a secondary source.

NATIONAL ACADEMY of SCIENCES: "The theory of evolution has become the central unifying concept of biology and is a critical component of many related scientific disciplines. In contrast, the claims of creation science lack empirical support and cannot be meaningfully tested."

Comment by Zachriel — March 2, 2007 @ 4:50 pm

Evidence

18 Responses to “Evidence”

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