February 24, 2009

Proof against Evidence

The last few days have been very busy. Started my Java programming project on Saturday, finished it before the deadline on Sunday. Have had other work to do and still have to send quite a few email to people who are probably wondering why I still haven't written back. So right now, I really shouldn't be writing a new entry for my blog. But I've had several ideas for a blog entry this week, and I just felt I HAD to write something. Oddly enough, what I'm about to write isn't one of the aforementioned ideas, but something that popped up tonight.

I had heard that there was this Grill-A-Christian thing in Knighcote (my residence hall), where you could ask a panel of christians any questions you had about their faith. I wasn't intending to go, not because I didn't want to (discussions like that are usually quite interesting) but because I just felt I had better things to do tonight, like sending those emails and tidying my room; but in the end I was lured by the Christian Union's free pizza. I never eat pizza during term-time, except when it's someone's birthday, or when it's free.

Anyway, it was very entertaining, and at the same time interesting and thought-provoking. I asked a lot of questions, trying to be inquisitive and raising challenging problems without sounding too accusing. The issues covered during the session isn't what I want to write about, though; this entry concerns two words that were used interchangably in relation to a particular question: namely "proof" and "evidence".

Before we go any further, let me point out that this is not a topic about religion or God: it's about the improper use of language. If I see a controversial comment bringing up this subject, I might well delete it, lest it will cause a flame war in a completely inappropriate place. If I fel I can get away with it, I might write an entry on faith, and my faith in particular.

When discussing God's existence, several talkers on the christian panel made use of the words "proof" and "evidence" as if the two were synonyms, and in fact meant the same thing. This is NOT the case: proof is stronger, a lot stronger, than evidence. If you have evidence that X is true, you have facts that make X more probable than previously believed, whereas if you have proof that X is true, the truth of X is then established beyond doubt. Briefly, given evidence, the truth or falsehood of X is still uncertain; given proof, it is certain. Strictly speaking, proof is only possible in Mathematics or other systems that employ formal logic to a given set of axioms (like theoretic economics), so a more relaxed version of the word is usually used in normal speech: Proof when when something is shown to be true beyond reasonable doubt. In other words, if X is proved to be true, only a complete moron* would blieve it to be false. You can have evidence for and against something in the same time, but you cannot have proof "for and against it" simultanously. There is either proof or disproof. Or neither.

To take a concrete example: If Shaggy's girl hears the screams getting louder, then later sees the marks on Shaggy's shoulder, she has strong evidence that he is banging the girl next door. Nevertheless, there is still room for doubt, and Shaggy can still pretend it wasn't him. However, if she catches him on camera, then she has proof (as long as she is able to recognise him in the video), Shaggy's lame excuse breaks down, and we will be forced to admit his infidelity. I think I've made my point. Please use the right words when you speak.

*In the case of physics, it's a little more delicate. Some things, such as light being a wave, had been "proved", until some genius found an anomaly and came up with a more suitable explanation

Now that we're here, I'd also like to address another vocabulary issue that crops up in debates about religion. Who hasn't heard creationists accuse the Theory of Evolution of being "just a theory". Again, I don't want to enter a discussion about Intelligent Design, I simply want to point out the meaning of the word "theory".

The word "theory" has two meanings, a scientific meaning and a normal-speech-meaning. The problem is that some people use the latter, when in fact it is clear from the context it should be the former. The common way of understanding "theory" is as a synonym for "hypothesis" or "conjecture", i.e. something unproven. It is a speculation that has come to life but that has not yet been verified by anything practical. There is nothing wrong with this definition: it is indeed what "theory" means in normal speech. But when dealing with the Scientific Method, "theory" has at least one other meaning: A collection of explanations that has been studied in detail, compared with actual data and approved by the general (scientific) community as being true, thus elevating the rank of the "Theory". A good example is the Theory of Gravity, or the more fancy-sounding Theory of Thermodynamics. In the context of the "Theory of Evolution", the word "theory" has this same meaning. It has nothing to do with the unproven connjecture of the alternative meaning. But ID proponent just never seem to realise, do they.

I'm on a roll now, I'll just mention something I read on a bag of The Stamp Collection crisps, today in Tesco's. It went something along the lines: "Terence Stamp spent years trying to find a recipe for gluten free crisps. And, being a master in the kitchen, we knew he would succeed." I'll give 5 pounds to the first person to spot and clearly state the grammatical error in the second sentence.

Oh and I just remembered this. Printed on a tuna sandwich I bought:


Oh for the love of Mike, please check for typos before you print something on a million sandwiches!

Phew, that felt good. I'm done ranting. Already two rants on my blogs, and they're BOTH about language. I have the feeling I'll be comlaining a lot about stuff like this. To be honest, I've got more in mind, but I thought it would be a bit of an overload. I'll try and make the next entry more positive, promise.

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  1. Chris May

    I’m not sure that

    approved by the general (scientific) community as being true

    is necessarily the case. I’d go for something like

    approved by the general (scientific) community as being a consistent model, capable of making accurate predictions about its subject.

    The notion of ‘truth’ in science is a tricky thing to pin down, it seems to me. The best we can do is to use ‘true’ as a synonym for ‘not yet disproved’ – but in doing so we’re freely admitting that things we assert to be true today, may turn out tomorrow to have been false all along; there’s no concept of a scientific truth which is eternal.

    ‘Religious truth’ sidesteps around this problem by requiring a different standard of ‘proof’; rather than relying on theory and evidence, a wide range of things are taken to be axiomatically true. That God exists, for a Christian, isn’t something which might be disproved tomorrow; it is ‘true’ in a much more permanent way.

    25 Feb 2009, 12:12

  2. Yay, I’m pleased someone actually read the whole thing! And you’re absolutely right, it is slightly problematic to call a scientific theory “true”, as it raises numerous philosophical issues. For something that is, by its very definition, scientific, Science is surprisingly good at asking metaphysical questions. As you said, one way of dealing with scientific truth is to accept that the actual theories are valid because not yet disproved, but may turn out to be wrong. And indeed, some people believe that Truth may never be reached in Science. Another approach could simply be to assert that we have reached our goal, and that our current theories are the ultimate truth. Which is a bit naive, but a logically valid belief nonetheless. And again, I suppose you could view it all from a third perspective altogether…

    Let me just be smug and point out, that Maths is arguably the only area in which we may discover absolute Truth. :p

    05 Mar 2009, 23:23

  3. Chris May

    Hold your smugness for a second, whilst you consider whether Maths thinks that it’s “true” that the barber who shaves all those who don’t shave their own beards shaves his own beard or not (and Incompleteness more generally). It turns out that even Maths’ truths have their limits :-)

    06 Mar 2009, 11:37

  4. Ugh! You just hit Maths right in the crotch.

    For the barber’s case, I’d argue that the question itself is meaningless, as the term “barber who shaves all those who do not shave themselves”, by its very definition, doesn’t make sense, in the same way that “a triangular circle” is nonsensical. (In relation to the mathematical version of Russell’s paradox, this is like saying that you can’t construct the set S containing all the sets that do not contain themselves, because it would have to be a subset of Ω, the set containing all sets, but Ω doesn’t exist. And only in Naive Set Theory is it assumed that S has to exist).

    But yeah, Incompleteness more generally. Is the Axiom of Choice true? Is the Continuum Hypothesis true? Is Zermelo-Fraenkel set theory, or maths in general, consistent? No-one knows, and it is impossible to prove or disprove – not just impossible as a manner of speaking, but literally. Yes, even Maths’ truths have their limits. Some say that there are statements in Maths (like the previous ones) that are neither true nor false; I prefer to believe that everything must be either of the two. Inherently. Even though we’ll never know which.

    All this reminds me of a joke I read some time ago:
    -The Axiom of Choice is obviously true, the Well-Ordering principle is obviously false, and as for Zorn’s Lemma, who knows?

    07 Mar 2009, 13:46

  5. dsch

    “And, being a master in the kitchen, we knew he would succeed.”

    The opening participial phrase does not refer to the subject.

    5 pounds please! :)

    23 May 2009, 16:47

  6. Sweet! Someone actually bothered to take up the challenge! Well done dsch, that’s precisely it!

    You deserve your prize. Heck, for actually reading the entire post in details 3 months after it was posted, you deserve more than a fiver. Send me an email if you want your reward. I’m sure we can figure something out.

    23 May 2009, 19:49

  7. dsch

    Haha, I was actually looking for the French verb to use for “I know kung-fu”, and was entertained by your posts (there should be more of them!).

    As for the fiver, the banks would probably gobble up most of it in fees and exchange rates, so feel free to donate to a charity of your choice.

    23 May 2009, 22:44

  8. You are completely right. As a Mathematician I got very irritated by the Christians in the Loxley Grill-A-Christian the previous year who dropped the word “proof” in everywhere while nothing is actually proven. Especially when they say something, make one small and reasonably acceptable step, then make one giant illogical leap to “prove” their point. For example, the Big Bang Theory doesn’t explain everything (I agree). Therefore isn’t true (I agree in that I think that science in general is just our best guess and it will be tweaked, details will be added, and the whole idea occasionally scrapped as new evidence comes to light). Therefore Genesis is correct (Erm, how?). Incidentally, I’m also a Christian and mentioned this to some fellow Christians this summer, who very stubbornly failed to get my point. These non-mathematicians, honestly! :p

    28 Aug 2009, 01:27

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