This is a good question. I gave the lost keys analogy as part of a reaction to the pessimistic argument that since past scientific theories have turned out to be wrong then its likely that present scientific theories will turn out to be wrong as well. My reaction is that we may be learning from our mistakes and indeed we cannot discover the truth immediately but must try things out and eliminate what turns out to be mistaken. In this case, a history of false theories does not show that present theories are likely to false; indeed it may make it more likely that they are true. But what if there is no key? Your point I take it is this. Sure, if we know that one of a group of competing theories is correct, and we can rule some of them out, then this will increase the probability that one of the remaining theories is true. But maybe none of the theories we consider is true. In that case, no amount of elimination will expose the truth. Clearly, if no theory we will...

You are right about proof. No scientific prediction can be proven from the scientific data, since it always remains possible for the data to be correct yet the prediction mistaken. The same goes for scientific claims about unobserved causes in nature. But it doesn't follow that we have no reason to believe these claims. I can't prove that my keyboard isn't going to burst into flames in the next minute, but I do have reason to believe that it won't. Admittedly, the great David Hume gave an argument that we have no reason whatever to believe that my keyboard will remain unignited for the next minute, but the fact that scientific claims are not proven still does not in itself make them any more speculative than my belief that I'm not going to burn my fingers.

Here is another way in which the normative and factual mix in the philosophy of science. One of the central normative issues is whether we are justified in saying that our best scientific theories are (at least approximately) true. The best known argument for saying that our best theories are true is the miracle argument, according to which the truth of our best theories is the only account that avoids making their remarkable predictive successes miraculous. The best known argument for saying that our best theories are not true is the pessimistic induction, according to which the fact that so many of the best theories in the history of science have turned out to be false (even when they were predictively successful at the time) makes it very likely that our current best theories will turn out to be false too. The miracle argument and the pessimistic induction address the normative question of whether we are justified in believing our best theories to be true, and they depend on factual claims about the...

As David says, replication in science is a way of checking that a result is genuine. We can distinguishing two different senses in which a result may fail to be genuine. One is that it was made up. Replication is a good way of detecting (and discouraging) fraud. Here there is a parallel in the study of history. If one historian makes a claim about what has been found in a document in an archive, other historians may want to check that this is what the document really said. But in science there is also another sense of 'genuine' that gives another reason for wanting replication. Scientific results are usually not just reports of what the meter said. They are often causal claims, like the claim that a certain drug reduces cholesterol. That claim may be based on an experiment where people on the drug ended up with lower cholesterol than people not on the drug. But that doesn't prove the claimed result, that the drug really does lower cholesterol. It might be that there is some other...

The discovery of ways to reliably produce fire was a great achievement in technology and engineering. The first observation of fire is not what I would call science (and presumably predates the existence of humans). But there is no sharp border between ordinary observation, inference and explanation and science, though there are clear cases on either side.

Since technologies are designed by humans and for humans, it is difficult to see how they could avoid the human element, at least twice over. Moreover, technologies have unintended consquences that also influence us, sometimes in profound ways.

It's not going to be possible to deduce intelligent design from scientific evidence, but no scientific theory can be deduced from evidence, only more or less supported by it. And I agree with Richard that there could in principle be good evidence for the existence of an an intelligent designer. Of course we have such evidence all the time for the human case. For example, archeologists working on a dig have to decide whether a given object is likely to be a natural product or a human artifact, and they often have excellent evidence for the latter hypothesis, i.e. for intelligent (human) design. But an inference to a non-human and perhaps divine designer seems crucially different in a number of respects. First of all, we have loads of independent evidence for the existence of human intelligent designers, but not for extra-terrestial or divine designers. Second, there really is no other remotely plausible explanation for the existence of say a finely wrought neclace than intelligent design,...

This question is at the heart of David Hume's great sceptical problem of induction. He argues that there is no possible reason for saying that the laws of physics won't change overnight, since to say this would be to make a prediction, and our method of prediction just presupposes that this won't happen. Put another way, it looks like you can't have evidence that the future will be like the past, because all your evidence is in the past, so to use that to show something about the future would require that you already know whether the future will be like the past. There has been a great deal of productive work on the problem of induction, but nobody has come close to a full solution. If you want to get into this great issue, the best place to start is Hume's classic discussion in his Enquiry Concerning Human Understanding , especially sections IV and V.

We are a very small part of the universe, and our best shot at figuring out what it is like involves making ourselves as causally sensitive as possible to the rest of it. That is what scientists do, through careful and sophisticated observation and experiment. If we are lucky, this will give us good reason to think that some of our scientific theories about the world are along the right lines. There is a very different way one might go about trying to figure out what the world is like, and this is by consulting an answer book that just tells you. Some people believe that their favored religious text is such a book. But we would need some good reason to believe that their text is reliable answer book, some good reason to trust it, and no such reason is available. Of course that won't dissuade someone who is convinced that they do have a reliable answer book, but they don't have good evidence for their view. To put the matter more externally, practices that depend on careful and...

When you ask for an explanation, you usually already have a justification. You want something more -- understanding -- which is what an explanation provides. Thus when you ask why the same side of the moon always faces the earth, you already know that it does, but you do not understand why. Much of the work in the philosophy of explanation can be seen as attempts to say what takes you from knowledge to understanding. (By the way, the reason the same side of the moon always faces the earth is not because the moon is not spinning. In order for the same side of the moon always to face the earth, the moon has to spin around itself with exactly the same period as the period it takes the moon to orbit around the earth. Spooky, eh?)