This case study reports on the progress of Navon, a 13-year-old boy with prelingual deafness, over a 3-month period following exposure to Logo, a computer programming language that visualizes specific programming commands by means of a virtual drawing tool called the Turtle. Despite an almost complete lack of skills in spoken and sign language, Navon made impressive progress in his programming skills, including acquisition of a notable active written vocabulary, which he learned to apply in a purposeful, rule-based manner. His achievements are discussed with reference to commonly held assumptions about the relationship between language and thought, in general, and the prerequisite of proper spoken language skills for the acquisition of reading and writing, in particular. Highlighted are the central principles responsible for Navon's unexpected cognitive and linguistic development, including the way it affected his social relations with peers and teachers. (Contains 1 table.)