A Study in Scarlet
"It is a capital mistake to theorize before you have all the evidence. It biases the judgment."
Most of you are probably familiar with Sherlock Holmes, either through feature films, television, or the writings of Mr. Doyle. He's a very prolific character when it comes to the ideas of deductive reasoning and critical thinking, but he's still a fictional character. Now most people would think that this is a well known and accepted fact, but there are some from our past and even those today, who do not know this. I have had to point many people to all the factual evidence that shows that no man by the name of Sherlock Holmes ever lived. But there is a good reason that many believe him to have been a real living man.
You see, as a physician, Dr. Doyle enjoyed knowing many important people. Among those is another physician named Dr. Joseph Bell. Dr. Bell was an esteemed colleague of Dr. Doyle, as well as a mentor. It is quite obvious that Holmes embodies a great many characteristics of Dr. Bell, including a propensity for logic and critical reasoning. In the dedication of the novel The Adventures of Sherlock Holmes, Dr. Doyle says of Dr. Bell, "You are yourself Sherlock Holmes and well you know it," which most definitely shows that Bell inspired the character of Holmes. But this doesn't mean Bell was a cocaine addicted, violin playing, Batmanesque crime fighter. Indeed, history tells us that Bell was nothing more than a common physician with a high intellect and a passion for deduction and logic. A man after my own heart to be sure - but he's no Sherlock Holmes.
The Sign of Four
"I never guess. It is a shocking habit — destructive to the logical faculty." 
It is common for us as humans to believe rather than to know. People tell me every day that they know Jesus was a real man and that they know the things he's famed to have done are true. They've not studied the evidence, nor made a logical deduction based on the evidence. They believe what they've been told and know very little if anything about the topic. Because of this belief that masquerades as knowledge, they make the shocking mistake of guessing to fit preconceived notions. They believe in the authority of some men's words, not based on the evidence that supports the veracity of their claims, but based on the claims themselves.
Evidence eliminates the need for guessing and it makes an uninformed supposition into an educated guess that is supported by the evidence. With enough evidence no guess work is needed. It speaks for itself. In the case of Sherlock Holmes we need not make any guesses. We know that no such man ever lived. We know he is a character of fiction who, although embodying many qualities of an actual man, had no more real substance than Batman.
But the case with Jesus is not so cut and dry. We have a great deal of evidence, but we don't have enough to know for sure. It is highly probable that a Jewish man once roused the Roman world with a new doctrine of religion. Indeed, this was a fairly common event. But we can not substantiate many other claims such as the "miracles" attributed to this figure of Jesus. More importantly, we can not pin down one singular historical Jesus based solely on the evidence at hand.
The Adventure of the Speckled Band
"When a doctor does go wrong, he is the first of criminals. He has the nerve and he has the knowledge."
The quote above could be said of the priest or " holy man" as well. You see, these men were once considered healers. They meant to heal body and spirit, and to heal the body through the spirit. An unclean spirit was believed to lead to an unhealthy body. As science came on the scene and started giving logical reason based answers for maladies, they began to get edged out. An area where they once had control was being taken away, but having the knowledge of how to control others, they set out to do just that.
What they thought of as spiritual well-being, we now understand as emotional and mental health. Our understanding of this takes away yet another arena that the priest and "holy man" once controlled. The only arena they have left is the "supernatural". The only claims they can still hold to are those which can't be shown false through evidence. So it has become of great importance for them to show proof of an historical Jesus. Because surely if the man lived, the "miracles" must be true.
The truth is that it is far more likely that the figure of Jesus is an amalgamation of many "prophets" of the time. And that his "miracles" are embellishments meant to bolster unsubstantiated claims of a fantastic and impossible nature. If we go by only the evidence, we can not say we know for sure one way or the other. There are contradictory accounts and a lack of evidence where we would expect it to be abundant. What we can say is that there is no evidence that the bible is a completely accurate historical record and we must strongly question its validity and contents. It is not proof, but rather is the claim which must be weighed against the evidence.
In nearly 2,000 years we've witnessed no miracles. What were once believed to be miracles have been shown to be natural or simply a trick of the mind. We have seen that the supernatural can at best not be quantified, and at worst is absolutely impossible. And as Doyle once wrote: "When you have eliminated the impossible, whatever remains, however improbable, must be the truth."