Here's the place that AC Doyle ran into trouble: more than one explanation can fit a fact. When Sherlock and Mycroft compare notes on the gentleman walking by in the street, they speak with definiteness that a particular gait can only come from having been at sea, and the only possible explanation for his carrying certain items is that he has children. Or, when Sherlock notes that a particular form of the letter "a" used declares the writer to be German, and of a certain height, it all ties together so nicely. The possibility that the man (or women) had a German schoolmaster who forced him to write that way, or that he reverted to that form because he slipped and had to make the accidental line into something, simply does not come up in the reasoning.
It is a comforting fiction, that we can read a set of clues which point us to a single answer, but real life isn't like that. All evidence is ambiguous and could point in several directions. It is the accumulation that points us in a direction.
It stems from our preference for resolved narrative. Reading a story of a woman who had an unhappy childhood and difficult life for 75 years, who found love, or meaning, or acceptance over the last five years of her life strikes us as a good life. It's a good story; it would make a good movie; therefore, it is a good life. The woman who has 75 wonderful years but ends it being sick or lonely the last five years seems to be a sad story, and a sad life. Funny thing. We rather think that even when it's our own life we are talking about. The drive for resolution is powerful. But if you had to choose going in which scenario you wanted, most of us would take the one with the good 75 and endure the lousy 5 as a small offset.
In mentioning The Moth, and relating it to testimony Sunday, I saw this same phenomenon. We insist that our life be understood as some sort of story, that it is going somewhere. Some of us feel at some deep level that belief in God necessitates belief in a narrative or trajectory of our lives, which we are tasked with discovering and enacting. I don't know that this is actually true - we just think it. Jesus's command not to be concerned for the morrow or what we should wear, but to let the day's trouble be sufficient unto itself, would likely speak against that interpretation.