[Ran-Taro]

Originally posted by Lord Chane:
Yes, it makes sense. But I still don't agree with the original statement. Let's go back to that for a moment. The assertion was "In the absence of any evidence of something existing, it is a logical presumption that it probably doesn't exist." I don't believe that's a logical conclusion. If we are talking probability, then the absence of evidence may mean that there's a low probability of existence, but as you already admitted it doesn't mean it doesn't exist. However to even calculate the probability of a given statement being true you have to have some information and that information constitutes evidence in and of itself. Going back to your example about predicting a die roll ahead of time, you can only calculate the probability if you know how many sides the dies has. My point is that you cannot calculate a probability when there is no data to base the calculation on. I believe the assertion also violates the laws of algebra. Look at the assertion as a boolean statement. You can evaluate it as X = Y. If so, then Not X = Not Y. In other words, if the absence of evidence means that the hypothetical item doesn't exist, then the absence of evidence that the hypothetical item doesn't exist must mean that it does exist. The two cancel each other out and therefore no logical conclusion can be made because there is no data to support a conclusion either way.

The problem with this idea (as I see it) is that it gives equivalence between entirely fanciful ideas, and reality as we know it.

For example, someone mentioned that an invisible pink Unicorn might be looking over your shoulder right now. Now let’s say that every time you misplace something, it is the invisible pink Unicorn hiding it. You can never prove it though, because the unicorn only does it when it can’t be seen. Hence you can’t disprove the theory either.

Certainly that might be true. I think we can (logically) say it is probably not though. The reason we can say so is precisely because it is logical to treat un-disprovable fancies as less likely to be true than physical realities that have been established through the weight of evidence. For example, that people misplace stuff.

In terms of mathematics, we can look at it this way. How many possibilities are there in the universe? Obviously, the answer is a very large number. In comparison how many of these possibilities are actually true? From observation of how many fanciful speculations we can generate about something, and then how many of those will turn out to be true – a very small number. Hence to generate a probability of the possibility being true (without evidence), we need a formula something like

X/Y = Z

Where X = a very small number of true possibilities
Y= a very large number of total possibilities
Z = the likelihood of a given possibility being true (without any evidence).

As you can see Z ends up as a very small number, and hence there is a very small probability of any given unfounded speculation being true.

Now, I am not for a second saying that this formula is absolutely valid in mathematical terms. However I am saying that it demonstrates a valid, logical principle in a simple form.

To compare it to the dice example – we might imagine that reality is a giant die, with an almost infinite amount of sides. We don’t know how many sides there are, but we do no there are a lot of them – because we know there are a lot of possibilities in the universe. Hence if we choose one of those possibilities (in this case ‘a single side of the die’), and logically predict how likely it is to be true, we can fairly say it is probably not true.

Now, your response to this might be to say that we are only comparing two possibilities (that there is an afterlife, or there is not), and that therefore the total number of possibilities in the world should not come into it. However this is not true.

The reason for this is that we are actually comparing something that is borne out by physical evidence (that when we die, we are dead) with a an unfounded speculation which circumvents it (that there is an ‘afterlife’ so that we are not actually dead when we die, but that this afterlife takes such an intangible form that it cannot be disproved). How many fanciful speculations can we come up with? How many of them will turn out to be true? The comparison between these two values will give you an idea of the probability of such a fanciful speculation actually being true.

Yes, my example of Pluto is skewed by the benefit of hindsight. But that was exactly the point I was trying to make. Following the assertion that was given, the statement that Pluto does not exist would have been "logical" if it had been made in the middle ages but would not be so now. I believe that shows a flaw in the assertion as demonstrated by the fact that Pluto does exist. A person making the statement in the middle ages simply did not have enough data to form a conclusion.

That is not true at all. The assertion only says that it is logical that a person making a wild guess about anything is generally unlikely to be right. It doesn’t say that they definitely won’t be right. If they do happen to be lucky, that doesn’t make the assertion wrong.

To think about it a different way - Imagine someone in 1200AD saying

“There is an eighth planet in our solar system, and it will be named ‘Pluto’ by someone in the future who actually discovers it. I have no idea why I am saying this at all, but I am, so there”

for no reason (ie, without any evidence). Out of all the things they could possibly think of to say for absolutely no reason! how likely would they to be to say this? I say it is not very likely.

In fact it is very unlikely that someone in 1200AD would with no evidence, and for no reason make a total guess about the nature of our solar system, and be right!. The odds against it are almost inconceivably high – perhaps worse than the odds of me guessing the number of planets around alpha century.

Hence if a person did make such a guess it is logical to say that they would probably (but not definitely) be wrong. In your example, they would have just beat the (enormous) odds.

Your example is a bit like if I said that, logically, by buying one lottery ticket you are unlikely to actually win the lottery. Then you say: but this person bought a lottery ticket and they won. It doesn’t change the fact that the odds were against them when they bought the ticket.

Hence, the fact that you can retrospectively put invent a scenario in which an incredibly unlikely event hypothetically occurred, does not mean that fanciful theories are logically (and statistically, and in terms of probability) as likely to be true as not.

Down through history there have been lots of statements made that were later proven to be wrong. That's because they were themselves wild speculations made in the absence of supporting evidence. Without supporting data any speculation, whether for or against, constitutes wild speculation. Is there evidence of an afterlife? No, not that I'm aware of. Is there evidence that there is not an afterlife? No, not that I'm aware of. How then can I draw a conclusion? If there's no evidence either way, then a belief in either has to consitute faith and faith is not a logical conclusion. It is an emotion, a desire for something to be as we want it. I see logic in this context as an outcome that can be consistently arrived at based on a given statement. For example, if a person is dead, then they are not alive. Since the assertion made seems likely to produce as many wrong conclusions as it does correct ones, I can't see it as logical.

The thing is though – the idea that when we are dead we are dead, and not alive, is not a wild speculation at all. It is the facts as we know them, backed up by all the physical evidence we have. It may not be the whole truth. However any unfounded speculation that goes beyond what we know must be weighed with the possibility that of all the many possibilities in the world, against the amount of them that actually turn out to be true, without there being any evidence for it. This is a question of probability, it is just harder to see it, and harder to quantify it. But it is quantifiable this far: As ‘unlikely’

Hence if someone asks me if there is an afterlife, I say probably not – unfounded speculations are unlikely to be true. However, if you want to know whether it is a matter of faith that when we are dead, we are really dead - go look at a corpse. Until someone provides some evidence otherwise, that is all the truth there is.

I see the Alpha Centauri example as something entirely different. It's an exercise in probability. The liklihood of you guessing the correct number of planets and the number of those that contain sentient life is indeed very low. Probably about the same as me picking all the lottery numbers. At the same time the assertion would mean that there is probably no sentient life anywhere else in the universe. After all there is no evidence of it, therefore it probably doesn't exist. This despite the fact that in this instance probability is in our favor. With billions upon billions of stars, countless millions of galaxies, it is inconceivable that we are alone.

As you can see, I see all of the examples as ones of probability, hence why I used that example.

The question of sentient life elsewhere in the universe is also one of probability. The reason you think it likely is precisely is that you do actually have some evidence. That evidence is that we know that the universe is very large, with many variables, and therefore there is definitely a possibility (in your opinion, a probability) that conditions conducive to life exist and have produced it elsewhere. If you were to start taking random guesses as to what form that life would take (without any evidence), you would probably be wrong, though.

Ironically, this is the exact reason why an unfounded speculation is unlikely to be true – the universe is so large and complex that there are too many potential truths out there fore a specifically unfounded speculation to be likely to be true.

Even though I don't agree with the statement made I appreciate such discussions. I've spent all week thinking about this topic. Very enjoyable.[/QB]

I too, enjoy such discussions, as long as they don’t get caught up in semantics, or become abusive. Thanks for providing me with some great mental exercise! I do enjoy it.

Look forward to a response, if you have one!