Summations Only

No. Dogs born without webbed feet don't get them later in life because they swim in the sea. Dogs born without webbed feet will die without webbed feet.What happens is that a dog is born with webbed feet, due to a random mutation. As RAZD pointed out, mutations causing webbed feet are common in humans and dogs. The mutation isn't a response to the sea being there, it's totally unconnected.Where the response comes in is selection. Do dogs born with webbed feet have better reproductive success than those without? If that is the case, then webbed feet will become common.

You're misunderstanding. Mutations do no happen in response to the environment.Mutations happen all the time. Whatever is going on in the environment, every single organism ever born has many mutations.Most mutations have no noticeable effect. Some do. Some of these effects are harmful. Some are good.And this is where the environment comes in. Whether a trait is harmful or good depends on the environment.Let's take a real world example. These are guppies (Poecilia reticulata), a very popular aquarium fish because you can breed them in all sorts of pretty colours. The plain one of the left is a female. The pretty coloured one on the right is a male. Now, let's say a guppy is born with a mutation that makes him brighter and more colourful. This isn't in response to the environment - it's just an error in copying his parent's genes that happened before he was born.This bright colourful guppy stands out for a mile, and he is noticed very quickly by a big hungry fish, and becomes lunch. He doesn't pass on his bright colourful genes. His mutation was bad, and the environment, in the form of a big hungry fish, determined this.Now, let's imagine that another guppy has been born with a very similar mutation, but he is born in a different place. He's born in a quiet little stream somewhere, where there aren't any big fish to eat him. This bright, colourful guppy grows to be big and strong, and all the lady guppies think his bold, bright colours make him look like a big hunk of gupy man flesh. This guppy becomes a player, sleeping around with all the lady guppies he can get his fins on. He leaves a trail of baby guppies all over the stream, meaning that the next generation are full of bright, colourful guppies like him. In this environment, his mutation was a good thing.The environment didn't cause either mutation. The mutations just happened. It's just that whether or not the mutation turns out to be a good thing and get passed on, depends on the environment it appears in.

The premises are not really contradictory - you should be reading the 'or' as an 'either-or' proposition. It's not meant in the sense 'sometimes it's this, sometimes it that'. It's like the following, valid argument:A: x is either an even or an odd number.
B: x is not an even number.
Conclusion: x is an odd number.Premise 6 is stating that the only three possibilities are regularity, chance and design. Premise 5 rules out regularity (I'm unsure why we're supposed to take this as given, or even what 'regularity' is supposed to mean in this context). Premises 3 and 4 are supposed to rule out chance (though Premise 3 is uncertain, and 4 is clearly false; unless I don't understand what 'specified' is supposed to mean). Thus, the only possibility remaining is design.The argument's perfectly valid, it's just based on false premises.----Expanding on the falseness, can anyone clarify what a 'specified event' is supposed to be in this argument? I'm not sure I understand the descriptions put forward. Events of staggering small probability happen with great regularity, simply because the sum of many probable events put together is a highly improbable event. The idea of specificity I get from the Wikipedia page is a bit vague, but it seems to be that there are not many other, also highly imporbable events that could have happened instead. If we look at the the final configuration of the Premier League, for example, it's staggeringly unlikely - but every other possible configuration would also be staggeringly unlikely, so it's not specified.But, if I've understood this correctly, then life is surely not specified. The number of different configurations in which life can arrange itself successfully can be seen by looking at the world, and the staggering number of ways it already does arrange itself. Different animals use a huge variety of different proteins to do similar or identical tasks, for example. What's specified about that?

The premises are not contradictory."A or B" means that either A must be true, or B must true. If neither of them are true, then we have a contradiction. If both of them are true, then we also have a contradiction. If just one of them is true, however, then there's no contradiction, and everything's hunky dory. (This all assumes we're using an exclusive or - in common speech 'or' can also mean 'and/or', but from context I don't think that's what zaius meant)This sort of argument is useful if the premises are actually correct. If it's true that either A or B must be true; and we have convincing evidence that B is not true; then logically this is convincing evidence that A is true; even if we have no direct evidence of that.