I've often been told that Jesus, rather than being the divine Son of God, was actually just a magician. As silly as this sounds, there are people out there who genuinely believe that this first century carpenter was not as special as He claimed to be. Rather, He had a few tricks up His sleeve.
In some ways, you can see why this argument is so effective. We see magicians active in our world, and so it is not especially unbelievable that they existed in the past. That does rather fly in the face of the belief that iron age men were superstitious primitives who would worship you if you so much as ignited a cigarette lighter, but hey, unbelievers never could keep a story straight.
The point of the above is that miracles, in order to be worth anything at all, would have to actually be miraculous. If it could be demonstrated that miracles had a basis in science, the above argument would hold up very well. Let's take Jesus' wine miracle as an example. Having taken a keen interest in magic for most of my life, I can think of a few ways this could be done. I don't even pretend to be especially skilled in magic, but a more legendary magician, such as Derren Brown, or Penn and Teller, could probably replicate this miracle without serious issue.
So, let's imagine turning water into wine was Jesus' only miracle. How convincing would this be? Not very. As soon as a miracle can be explained scientifically, it ceases to be miraculous, and thus it ceases to be convincing. If Jesus' only miracle was the wine thing, Christianity would never have gotten off the ground.
Next question: How many magicians do you see working in a hospital? Although some doctors do have some skill in magic, they don't use that to heal their patients, they use it to entertain their patients while they cure them with medical science. Medical science which, to this day, is not sufficiently advanced to replicate Jesus' healing miracles. You can't spit in the mud and expect a doctor to heal a blind guy. Leprosy doesn't just disappear with one touch. A quadriplegic cannot expect to be lowered into a hospital and walk out carrying his mattress because the doctor told him his sins were forgiven. These things just can't be done, and that is why miracles are significant. They are things that only God can do, and so they can only be explained by faith in God.
The most significant miracle Jesus ever did was rise from the dead. This miracle is the one upon which all of Christianity hangs. If it really happened, Christianity is true, and no sane person would reject it. If it can be disproven, Christianity is false, Judaism is false by extension, and there is no religion on the earth that is worth believing. But let's say it is neither proven nor disproven, but rather, it turns out there is a scientific basis for resurrection. Let's say just one other person, be it historically or in the modern day, can rise from the dead. Well now we have a problem. If resurrection is not something only God can do, unbelievers have the advantage. They can finally accept the evidence that points to the resurrection, and they can say "sure, Jesus rose, but so did Jerry, so what makes Jesus so special?"
As it is now, atheists dispute the life of Jesus by dismissing His miracles as magic tricks. If we could find scientific explanations for miracles, they would do this on a much larger scale, and it would actually make sense. Miracles, by their definition, are not scientific. Rather, they are supposed to be unscientific. Therefore, to ask for scientific evidence for miracles is effectively saying "I will not become a Christian until you prove I shouldn't become a Christian". In reality, the correct area to look for evidence of miracles is history. We don't look for scientific evidence that miracles can happen, we look for historical evidence that they did.
Thankfully for us, such evidence does exist. Aside from the historical aspect of the Bible itself (it would be circular reasoning to treat the Bible as less than the historical document it is), the sceptics of our time use different methods than did Christ's contemporaries. In the modern day, sceptics tend to stand more on the side of denial. Bart Ehrman, for example, once wrote "Over the years I’ve thought a lot about this question, and have tried to explain on several occasions why a “miracle” can never be shown, on historical grounds, to have happened — even if it did." (1)
In the past, however, sceptics were a lot less capable of doing this. Because so many people not only witnessed Jesus' miracles during His ministry, but saw Him alive and well after they saw Him publicly beaten and executed (not to mention the miracles the Apostles performed afterwards), sceptics would more often resort to attributing it to another source. They would torture, kill or otherwise persecute the witnesses, question their reliability (ad hominems are not a new thing) or attribute the miracles to another source, such as demons, or even just some kind of natural chicanery. Denial on the scale we see today is only possible because enough time has elapsed since the miracles in question occurred.
That miracles happened is open for debate. It is fair, and actually admirable, to ask for evidence. It is not, however, fair to limit the evidence you will accept, especially not when the very evidence you are asking for would better serve to refute the position you are criticising. Evidence is evidence, no matter where it comes from, and to deny it without reason is no wiser than to just accept it without reason. Science is not the correct field to search for evidence of miracles, history is.
Contrary to the claims of the aforementioned Bart Ehrman, the historical record amply testifies to the miracles performed by Jesus, including His resurrection. This is rather handy, since the resurrection is both the primary evidence for, and central claim of Christianity. If the Lord's resurrection happened, Christianity is a fact, and if we confess it, we will be forgiven of our sins and inherit eternal life.
References
1. Ehrman, Bart - Historians and the problem of miracle, Ehrman Blog, November 15 2013 (link)