In one of my last posts, I gave the opinion that most of the so-called "brick wall" claims in genealogical research were mostly fallacious. Of course, I immediately received contrary opinions. For that reason, I believe the discussion of the issue should be expanded. Genealogical research is not entirely open ended. As with all historical research, there are finite limits to the amount of information available in any given locality or time period. It is evident that in the current era, the amount and number of available records concerning individuals are both expanding at an increasing rate. In the future, there will be no lack of sources about almost anyone.
The general rule is that the number and availability of records about an individual decrease as you research back in time. If you go back in time far enough, say to the early 16th Century or even the 15th Century, it is evident that few if any of the surviving historical records deal with genealogical information about individuals other than royalty or other prominent people. There are exceptions in some cultures and societies, such as in China, genealogical records date back as far as the Shang Dynasty (1523 to 1028 B.C.).
European records do not have nearly so long a history. For example, the earliest surviving Protestant records from Germany are from 1524 at St. Sebald in Nürnberg. Lutheran churches in general began requiring baptism, marriage, and burial records in 1540; Catholics began in 1563. By 1650 most Reformed parishes began keeping records. Some countries began keeping records as early as the 1300s, such as a few Catholic Parishes in Italy. The church records of Palermo, for example, start about 1350, and the baptistery in Firenze has records from the early 1400s. See Wiki FamilySearch for a particular country.
Knowing the limitations of the existence of records leads us to the conclusion that at some point, all genealogical investigations come to a dead end. The records simply do not exist. Even in China, the existing ancient records emphasize the male lines at the expense of providing very limited information about the female lines.
Another example is the fact that the civil registration of vital records, births, deaths, marriages and divorces, is a relatively recent activity. England began civil registration in 1837 and some of the U.S. states did not include birth or death information in their vital records until well into the 1900s. It is a fact of life that some ancestral lines will simply end when the records run out.
However, I do not think that this ultimate lack of written records is what is commonly meant by the use of the term "brick wall." It is my understanding that the issue of brick walls comes about a result of having someone who does not appear readily in the existing records during a time period when the records of his or her life should have been available. There is always a remote possibility that some very early records, generally unknown to historical researchers, could be found, but it is highly unlikely for that to happen.
There are also special circumstances which by their nature, do not lead to further research. It is extremely difficult to find the parents of abandoned children or sometimes for orphans. In some societies, the parentage of an illegitimate (born out of wedlock) child may be entirely obscured by the record when the birth is attributed to another, but married relative. Even in these extreme situations, there is always the possibility that further research either of the person or his or her immediate descendants, may reveal crucial information about parentage.
What I find to be a problem is the very issue of categorizing a lack of information with the terminology of "brick wall" thereby making the name itself somehow to blame for our own inability to address the investigation correctly and solve the riddle.
The reasons for an inability to make further progress is commonly due to searches in the wrong locality or for the wrong name. I do find a tendency among a significant number of researchers to abandon the search as soon as readily available records do not correspond to the researchers' preconceived idea of where or who the ancestor should be. It is one thing to come to the end of the line in the 1500s in England and quite another to be unable to find a family in Ohio in the 1800s. It may also be unfruitful to continue to spend time researching a transported immigrant in the 1600s. There are times when it is appropriate to come to the conclusion that all of the possible records have been searched.
Another observation, very few researchers have really searched all the available records. Again, most so-called brick wall situations involve inaccurate assumptions. I could give many, many examples just from the last few weeks of assisting with research, but that will have to be another day.