With the aim of discussing the relationship between writing and the cognitive development of illiterate adults, we carried out a (re)reading of Luria's research, a central reference among cognitive studies. Our main purpose was to clarify some of the historically established notions that underpin those studies, which focus on criteria from formal logic and show illiterate adults' cognitive deficits. Our analysis stresses the need, among other findings, to break away from traditionally established criteria that rely on formal logic. As a result, our study proposes a plural view of human rationality, that considers subjects' interactions among themselves and with the culture to which they belong, and which they modify throughout their lives. This study is part of a broader project which further develops our analysis of Luria's study. Starting from the assumption that rationalities are intimately linked to peoples' experiences and practices in culture, this project proposes to look at the rationalities of subjects at different levels of litteracy, when involved in a dialogic situation.