This thesis investigates the notion of *'writing as thinking'* or *'writing to learn'*. Based on Rumelhart et al.'s (1986) connectionist model of cognition, I argue that the main similarity between writing and thinking lies in their connection-making nature. **Knowledge-transforming writing** involves the creation of new connections between previously unconnected or differently connected propositions, during the process of writing, while **knowledge-telling writing** involves the transcription of previously rehearsed ideas. Drawing on Eugene Winter's (1974, 1979) work on repetition and Michael Hoey's (1991) work on lexical cohesion, I hypothesize that knowldge-telling is signalled by the presence of *intertextual repetition without replacement*, i.e. (near) identical sentences in texts written by different authors on the same or related subject, (near) identity being a function of the number of lexical repetition links between sentences. I investigate whether current instructional practice, as characterized by **source-based writing** and **peer collaboration**, ecnourages knowledge-telling, and whether knowledge-transformation is a key concern in **writing assessment**.