Successes and failures when learning to prove

In this article, we present some results obtained in a case study in which the arguments of a group of students, aged 14 to 16, were characterized, using Toulmin's model. The arguments were produced when, in a proving activity experience, they formulated a conjecture as the solution to a geometric problem and then justified it. Particularly, we show two moments in which there is evidence of the student's possible comprehension of what proving is and how proofs are constructed, process that was affected by two epistemic conflicts. The analysis of the arguments lets us establish successes and failures with respect to proof that were evidenced during the process.