This article is the result of reflection that emerged while conducting qualitative field research on nationalism and exclusion in Portugal. The problem I confronted was when to stop interviewing. Stated more precisely, I was seeking an answer to the question of when one has collected enough empirical data to support or reject one’s hypotheses. This initial problem led me to a rather old discussion on the difference between natural and human sciences that has characterized German academic life for many years–in fact, since the early 19th century–producing some more heated phases of academic dispute, known as the Positivismusstreit in the 1930s and the 1960s.