This comes on the heels of an earlier essay which was woefully incomplete and is not necessary for understanding anything I'm about to write. That essay was also about faith and science, and as one person pointed out, I defined my use of the former term too loosely, if at all. So, in part, the following is an attempt to present more clearly what I mean by "faith", and why I think that it is as essential to science as to any religion. This is by no means a criticism of science. Rather, it is an attempt to show that faith is something that every human endeavour requires, be it religion, astrology, engineering or physics. I would also note that this is a philosophical take on the issue, not a psychological one. I don't purport that anyone need actively and continuously hold in mind what I'm about to expound, merely that if they followed the reasoning out, they would come to roughly the same conclusion.
Imagine a scientist coming to a point in their research where the data goes awry. Checked and rechecked, it is surely accurately recorded, and the experiment worked exactly as planned, yet it conforms with none of their prediction, expectation or theories. Imagine that this scientist, convincing their peers that everything is legitimate, spends weeks, then months, then years attempting to find an explanation for the phenomenon, and, if dedicated enough, dying with it still the pressing matter on their mind. This is, of course, a caricature, as the scientist no doubt had many other projects and interests, but, in part at least, this does characterize some problems that have arisen in science. Einstein died without ever believing his own quantum results. Copernicus never knew of Kepler. Etc.
Such things have happened for centuries. Yet, why does this happen? Why don't scientists simply say, "well, we haven't explained it; must not be naturally explicable." Surely, if you haven't cracked it in your lifetime, its worth going to the grave with the smug assuredness that no one will be able to do so. Yet they don't. They proudly (or resignedly) leave it to future generations. In fact, it would seem that the entire project of science would break down if any scientist were willing to take this supernatural leap at ANY point!
One has to admit that if scientists were willing to admit that certain parts of nature were inherently inscrutable, they could never draw a line! There would either have to be nothing at all not amenable to the inquiries of science, or any arbitrary thing at all would have to be. If we're willing to say that the several seconds after the Big Bang can never be understood, why can't we say that other early cosmic events also can't be? And if those can't be, then later ones could surely have some totally obscure properties. And so on down the line to the dying of bees and the migration of whales. But science will never do this. There will always be some new theory, we assure ourselves, and if such a theory is not available, then some new discovery or insight is always around the corner. No matter how intractable a problem seems, scientists seem to have faith that some explanation will present itself in the near or distant future.
And here we come to the crux of the matter. Regardless of whether one would think it trivial to call it such --- or would argue that you need only interest and curiosity and nothing else to continue science, or whether you would say that there are purely practical concerns which drive research --- in order for science as a whole to go on at all, you have to have the faith that the next perplexing mystery you come across won't be the one whose solution is "God-did-it". No matter how bizarre, counter-intuitive, or contradictory results (and their consequences) are, you have to have faith that they will be explainable either as error or lack of understanding. Science proceeds by calm rationality, methodical care, and occasional brilliance, but beneath all this must be the foundation that there is no point at which it will run out of answers.
This faith need not be one blindly believed! It is entirely possible (and, in certain metaphysical views, quite likely) that science truly cannot provide all the answers about nature. (By "answers" I here of course mean correct predictions and coherent explanations, not unquestionable truths set in stone for eternity --- science does not deal in such things to begin with.) This faith may be entirely misplaced, metaphysically speaking, but even if this is so, science is still by far the best tool we have ever had to discover reliable truths about reality. In practice, it SHOULD be seen as an infinitely capable, all-powerful tool for explaining the world around us. I would even go so far as to say that this is exactly how it IS seen! Imagine any phenomenon in nature which is completely immune to the scrutiny of science; it is an impossible task! Even parapsychology and cryptozoology have their share of earnest researchers striving to do good science. However, philosophically speaking, science is only a conditional: IF everything in nature is explainable by natural causes THEN the following results will form a coherent, interlocking picture of all of reality.
Faith in some form is present in all human works. There is the prosaic faith of the engineer and architect that when the bridge is built, the laws of physics will work the same way they did yesterday (or, to be cliché, that the sun will rise tomorrow). But there are also deeper levels of faith in the world around us: that the other drivers on the road won't all decide that today is the day to drive on the left side; that you will be able to accomplish tomorrow what you trained to do today; that people who loved you yesterday will do so tomorrow. You may call it trends, probability, reason, natural law; but there will always be a deeply personal level on which you don't care about those things --- you just have faith that the world works basically the same way you've always understood it to work. And the vast majority of the time that's good enough.
THIS is the kind of faith that science relies on. Not faith is something mysterious, powerful, unseen, cogent. Just faith in our own ability to seek and find answers. Of course, many will read this and think, "he's still just using 'faith' wrong; faith is a [religious/feudal/emotional] concept that has nothing to do with careful observation and experiment; science is just the method of testing hypotheses and getting relevant results". But I think that the exact same emotion that drives believers to continue reading holy books and praying is what drives scientists to explore the bounds of reality by every (repeatably verifiable) means available. If some problems could never be solved, you would never be sure that you didn't hit that particular problem yourself, and were wasting your entire life trying to solve something truly intractable. To be a scientist, it seems to me, is to necessarily and implicitly have faith that, in practice, the entirety of nature is naturally explainable.
One final, key, point must be made: it is the moral obligation of science and scientists not to assume that they start with any absolute truths. Everything at all must be open to question and scepticism. This includes the very notion that the universe is completely explainable by science. For believers in the supernatural, faith is the principle that allows them to maintain their beliefs in the absence of evidence. For scientists, faith is what allows them to continue doing what they do without experiencing an existential crisis every time they hit a dead end. It is not some wishy-washy, I-believe-because-it's-true obstinacy, but rather the thing which allows them to make great discoveries in the face of contradiction, nonsense, ridicule and sheer exhaustion. It is a faith as pure and honest (and, with apologies, more useful) as that of any monk.
Perhaps I have not made my point entirely clear, as it is a fairly subtle one. Perhaps another day, if this attempt proves unsatisfactory.