Because there are so many individual manuscripts, textual critics are hard-pressed to know the individual characteristics of each manuscript. Consequently, many textual critics categorize the manuscripts into text-types, which they then use in their evaluation of textual variants.
Theories and Methodologies of New Testament Textual Criticism
Even though these various schools of thought can be identified, it is necessary to realize that some textual scholars might partially adopt the approaches of two or more schools, so that a synthesis often results. Likewise, schools tend to fluctuate over time due to the influx of new leaders and materials.