Imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for.
The 'Puddle Analogy' seems to me to be simple, funny, and somewhat unoriginal. What is its relevance to fine-tuning? The puddle, of course, fits its hole so well not because anyone designed it that way, but because the water it is composed of adapts itself naturally to whatever shape the hole takes. The analogy that this would have with fine-tuning would be something like the following: 'Life is adapted to the universe, and not the other way around, so if the universe had been different life would be too. In other words, a different kind of universe would have yielded a different kind of life.' If that's what the analogy means, then it is simply a funny way of putting the 'Other Forms of Life Objection' that we have examined previously.
The Anthropic Principle
Some have responded to the fine-tuning by simply saying, 'Of course the universe has to be just so to allow our existence. If it wasn't, we wouldn't be here to comment on it.' The logic used here is undoubtable correct: the universe must be able to permit our existence, since if it wasn't we wouldn't exist, and we do exist. But people sometimes take this tautology and mistake it for an explanation of the fine-tuning. And it isn't: Your existence is a result of the fine-tuning. It is NOT a cause of the fine-tuning. Your existence in no way caused the universe to be fine-tuned, so it cannot explain the fine-tuning.
I've heard people say that the fine-tuning argument argues in a circle because the very word 'fine-tuning' implies that one has already established that some agent did tune the universe. But that can't be assumed in the argument because that is the very thing to be proved: whether there was a conscious agent who rigged the laws of physics. I think this is a weak objection. It's a semantic point masquerading as something more. The phenomenon we describe as 'fine-tuning' could be described in less anthropomorphic ways: it could be called 'improbable life-friendliness' instead, for example. Nevertheless, the phenomenon we refer to as 'fine-tuning' or 'improbable life-friendliness' still requires an explanation, and we want to find the best explanation available. The best explanation could be a designer, or a more fundamental law of nature, or a multiverse, etc. And we will begin comparing these explanations in later posts.