As far as I know, the main argument for the statement that the universe is expanding is that the velocities of galaxies increase proportional to the distance. This together with the cosmological principle indicates that every point in the universe observes the same thing, something that is indeed a characteristic of space expansion. The orthodox view is now to conclude that these velocities are caused by the expansion of the universe. I.e. the galaxies moves --with the space--, not within it. This interpretation find support in the theory of general relativity. However, even though it is a characteristic of expansion, there seems to be no necessity that it must be interpreted that way. Could we not also interpret it as the movement of galaxies -- within space-- which just happen to have that particular velocity distribution consistent with Hubbles law? If not, what observational evidence is in favor of the former view? Are there any theoretical inconsistencies?