  In this paper, three plausible axioms together with two definitions are
employed to build an axiomatic framework, and then with the help of the Dirac
formalism, it is demonstrated that the time-dependent Schr\"odinger wave
equation is no longer a postulate for the whole theory, but a theorem.
Subsequently, a proof for the theorem is presented. The result implies that the
other remaining axioms of the picture essentially involve the Schr\"odinger
equation, and this consequence lets the whole theory become stronger.
