Current research in the plain language movement has failed to establish definitive criteria for document comprehensibility. Analysis of conventional approaches to comprehensibility assessment reveals a dichotomy of values, one objective, the other subjective. Because these two approaches have fallen short of providing any cohesive frame of reference, the author proposes that future research efforts be directed into a potentially supplementary one: document legibility analysis. Legibility is integrally related to the concept of comprehensibility. Because legibility analysis provides a point of synthesis for the objective and subjective modes of traditional research, it may also provide new insight into the delineation of factors affecting document comprehensibility.