  Some conceptual problems in physics are discussed. Do we need a change in the
concept of matter structure? Why the ``$i=\sqrt{-1}$'' is introduced to quantum
mechanics (QM) essentially? What is the relation between QM and special
relativity (SR)? Could we modify the stationary Schr$\ddot{\rm o}$dinger
equation in conformity with SR? How can a particle acquire a mass? We propose
some tentative answer. Their philosophical implications are emphasized.
