Single-case causality assessment as a basis for clinical judgment.

Current methodology of therapeutic causality assessment can be traced back to four underlying paradigms: (1) empirical scientific judgment relies on experimentation (paradigm of experiment), (2) causality assessment requires repeated observations (paradigm of large numbers), (3) observed results must be compared with results of control observations (paradigm of comparison), and (4) observed objects or patients must be distributed to verum and control group by chance (paradigm of randomization). Problematic aspects of conventional methodology and the historical evolution of contemporary causality assessment illustrate the necessity and possibility of methodological alternatives. A fundamental alternative is offered by figural correspondence and figural experiments, which allow valid causality assessments in single-case situations without blinding, randomization, comparison, or large numbers of observations. The epistemological foundation of such single-case causality assessment is explained. Examples from clinical judgment are presented. Single-case causality assessment may be particularly appropriate for therapy judgment in complementary medicine.