  We start from the simple fact that the method of images can always be used to
obtain {\Phi}_{\sigma} (r^\to_in), which is the potential inside conductor
produced by induced surface charges. We use this fact to construct image method
for outside potential {\Phi}_{\sigma} (r^\to_out). We show that if we can find
a relation between {\Phi}_{\sigma} (r^\to_out) and {\Phi}_{\sigma} (r^\to_in),
then the image method for {\Phi}_{\sigma} (r^\to_in) can be used to derive the
image method for {\Phi}_{\sigma} (r^\toout). The number, the position and the
amount of charge of the images can be directly derived. The discussion can be
extended to the general n dimensions.
