A generalization of Poncelet's continuity principle made by H. Schubert in 1874-1879. The conservation of number principle asserts that the number of solutions of any determinate algebraic problem in any number of parameters under variation of the parameters is invariant in such a manner that no solutions become infinite. Schubert called the application of this technique the calculus of enumerative geometry.

continuity principle | duality principle | Hilbert's problems