Understanding the role of induction, intensions and extensions in pragmatic clinical research and practice

Pragmatic clinical research methods are poorly understood, but essential to practice outcome-based medical or surgical care. Pragmatic research aims to verify the connections between medical knowledge and the reality of practice. Its methods can be understood by reviewing the problems of induction, as well as the related linguistic and mathematical notions of intensions and extensions.

We briefly review the source of problems with using inductive methods to gain knowledge, and the relationships between language, mathematics and reality. We discuss linguistic 'sense' and 'reference', and the set-theory terms 'intensions' and 'extensions', which define the relationship between individuals and whichever pertinent collection these individuals comprise. Both concepts are essential to understand pragmatic medical research and evidence-based practice.

Pragmatic clinical research can be explained in terms of testing (in reality) the repeatability of various inductive referential and inferential steps used in clinical practice - from reliability, diagnostic accuracy, and prognostic studies to pragmatic trials. All pragmatic studies aim to verify the relationship between the extensions of the notions of symptoms, diagnoses, prognoses, treatments, and outcomes. The concepts of intensions and extensions also serve to understand 'statistical significance' in analyzing trial results, as well as problems related to eligibility criteria and subgroup analyses. The results of clinical studies can be generalized to the extent that they have been tested in numerous and widely different individuals.

The notions of sense and reference, and of intensions and extensions, help explain the role pragmatic clinical research methods can play in optimizing care.