Accuracy of the quantum adiabatic theorem in its original form

An explicit proof is developed to reinforce the accuracy of the quantum adiabatic theorem in its original form without any inconsistency and/or violation. Based on this proof, we discuss physical implications that give rise to the violation of the quantum adiabatic approximation. We show that such a violation can be obtained if and only if one violates the adiabatic criterion itself or due to the existence of degeneracy at a later time. Subsequently, comparison of our proof with respect to other recently developed proofs and counter-examples are analyzed and discussed.