In mathematics, a reflection principle may refer to: Reflection principle, the principle in set theory that it is possible to find sets that resemble the class of all sets Reflection principle (Wiener process), a result about the distribution of the supremum of a Brownian motion Law of reflection, the principle that the angle of reflection of light from a surface is the same as the angle of incidence Reflection formula, a relation between f(x) and f(a − x) for a function f and a constant a Reflection theorem, one of a collection of theorems about the sizes of class groups Schwarz reflection principle, a way to extend the domain of definition of an analytic function
See also Van Fraassen's reflection principle, a philosophical principle