1) Theorem 
Bayesian refers to methods in probability and statistics named after Thomas Bayes (c. 1702–61), in particular methods related to statistical inference: These methods include: Bayesian also refers to the application of this probability theory to the functioning of the brain: ...
Bayesian: Pertaining to Thomas Bayes (1702-1761) and to probability methods based on Bayes theorem. As in Bayesian logic, Bayesian probability, Bayesian reasoning, Bayesian statistics, and so on. Now much used, the term 'Bayesian' came into use about 1950. See also: Bayes theorem.
adjective of or relating to statistical methods based on Bayes` theorem