The study focuses on how specificity of pediatric practice at the Fernandes Figueira Institute, Oswaldo Cruz Foundation, contributes to the development of clinical reasoning, the ability to detect evolution in serious illness, and the capacity to use diagnostic and therapeutic techniques. Data were collected using a thematic interview and analyzed by a semiotic model. The results showed a common view of medicine as both science and art, the doctor-patient relationship as legitimating medical knowledge, pediatrics as having its own peculiarities (thus being defined as a medical specialty), and a severity postulate that hinders the development of clinical reasoning and thus the ability to detect evolution in serious illness.