When I was studying drawing and painting at the university, the professor would project an image on a screen grossly out of focus. We would begin sketching and as we worked he would slowly bring the object into focus. The idea was to see the light and the dark and the general form of the object before focusing on details.
Genealogy is a similar search for patterns. But too often we ignore the patterns by focusing on individuals and events rather than looking at the larger picture where the patterns can be discerned and hence, we never see the pattern. Although each individual is unique, unless we understand how the individual's uniqueness functions in the overall pattern of the extended family, we may not be able to find the unique individual. I struggle with this each time someone asks me to find a particular individual. I try to help the researcher understand that looking for a specific fact or one individual may not be productive. To find the father, you may need to find the uncle. To find the mother, you may need to know more about the daughter. Nothing in family history happens in the vacuum. All of the family events are ultimately connected into the fabric of the family. Stepping back and looking at the whole picture may and will ultimately reveal more details than you thought were possible.
I can't tell you how many times I have approached someone and offered help to be told that they were looking for a ___________ (fill in the blank with marriage date, death date or some other date). Here is what I think. I think, how sad that this person has lost the individual and the family in details and yet, at the same time, I find myself caught up in the same trivia. I am not advocating ignoring the details, what I am saying is that until we know the general outline of the family history, the individual facts will take over and keep us from seeing how this family lived and died. Like the people I help who are looking for a remote ancestor, such as a great-grandfather, and when I ask them how they are related to this person cannot tell me.
Where did the family live? What did they do to support themselves? What contact did they have with their extended family? Who were their neighbors and were they related or unrelated? How large was the community? Was the family a newcomer or one of the old established families? What church did they attend? What kind of education did they have? Did they belong to any kind of social group? If you haven't guessed by now, each of these questions when asked and then answered leads to additional records about the family. If there are no answers to any of these questions then maybe you are looking for the wrong family or for the right family in the wrong place. Think about what you are looking for and expand you view to encompass these and many, many other relevant questions.
Just as I worked at drawing as the picture came more into focus, so as you look at the wider, perhaps out of focus picture, you will begin, over time, to see the real details of their lives, instead of looking forever for a marriage record that may not exist for the simple reason that the couple never got formally married.