This study investigates the role of existentials in the construction of medical knowledge and how they manoeuvre argumentation in scientific research papers. Corpus analysis reveals that some grammatical environments appear to be chosen on epistemological grounds since they are frequently employed in medical writing to encode and disseminate evidence-based information. Thanks to their semantics, existentials form a privileged environment in which to tackle medical discourse from a quantitative angle, especially as quantification represents one of the techniques of objectification characteristic of scientific writing. On the strength of their quantificational import, existentials, as they present themselves throughout a medical paper, can bring inherently argumentative intentions to the surface since they are used to justify the validity of the claims made by the authors of a clinical study.