An obviously hypothetical scenario: You are the only human being on the planet, nothing even remotely resembliing your intelligence has ever walked the planet. One day, you decide to take a walk and on your trip you find a watch. You cannot recall ever making this watch and no animanl has the mental capacity even close to the level needed to build said watch. Obviously the only possible explanation is that the watch came into existence of its own accord.
By now your probably laughing at me and saying "What a crackpot". But if we are able to assume that living beings that are infinitely more complex than this watch came into existence without the influence of some greater being, through random mutations that 99.9% of the time are harmful rather than beneficial, who are we to say the watch formation didn't happen of its own accord.
The study of an object can help you reveal the most likely processes by which it came to be. Given the fact that it is impossible for the watch to change other than through boring natural processes such as rusting, much less replicate itself, evidently another object or entity had to be involved in its creation. This excludes evolutionary explanations to its existence. Living beings are much more complex than a watch, but they can reproduce, they can mutate, etc. Given all the properties living beings have, we can determine the most likely process that could create them. And that process is, behold, evolution.
A watch looks like it was made by humans (or similarly advanced entities). Humans (and other living beings) look like they were made by evolution. Given a watch, you can infer the existence of humans (or similarly advanced entities); given humans (or other living beings) you can infer the existence of evolution.
BAM_UR_DEAD said:I'm not quite ready to enter the debate, but I'm just wondering what the hypothetical chances of abiogenesis ("something from nothing") are compared to creationism ("intelligent design" by a "creator God"). Both sides of the spectrum use the "well, the chances of your idea are so ridiculously small that my idea is much more plausible" argument (which is a fallacy either way), but both sides are also hard pressed to present their numbers.
The comparison is not fair because "intelligent design" by a "creator God" is ill-defined. The chances of abiogenesis are computable, maybe not in practice, but at least in theory. The chances of intelligent design are impossible to compute because there is no proper characterization of the entity which is supposed to have designed us, much less of how he would have done it. We would have to determine what kinds of entities can be gods, the probability of a god existing, the probability that he would even want to create life as we know it, and then the probability of him doing it in a way that produces the evidence we observe. Problem is, this requires God to be intelligible, which he often isn't by definition.
jamespicone said:And obviously it's impossible to calculate probabilities for special creation via supernatural power, but it falls victim to Ockham's Razor more than probability. It's far more parsimonious to have abiogenesis occurring as a result of already-well-understood chemical processes rather than as magic. Particularly because those pesky scientists start asking questions about how the magic works.
Ockham's Razor is a probabilistic argument. It places prior probability on all theories saying that simple theories are inherently more likely to be true than complex ones. Since the posterior probability of a theory is proportional to the likelihood of the evidence under that theory multiplied by its prior, if evidence cannot tell apart two theories, what remains is the prior.
More specifically, Ockham's razor says that "just X" is inherently more probable than "X and Y". If "just X" explains the evidence just as well as "X and Y", the former must be preferred. Y should only be considered in circumstances where its addition gives us greater explanatory power.