  Besides the defining space-time symmetries (homogeneity and isotropy) of
inertial frames, the derivation of Lorentz transformation requires postulating
the principle of relativity and the existence of a finite speed limit. In this
article, we point out that the existence of a finite speed limit can be readily
inferred from the nature of allowed inertial frames. We also show that the
principle of relativity can be obtained from the defining space-time symmetries
of every inertial frame. Therefore, if the conventional definition of inertial
frames is augmented properly, the special theory of relativity (Lorentz
transformation) would follow from the definition of inertial frames.
