Ludwig von Mises on the paradox of "planning"

We may admit that in its initial period a socialist regime could to some extent rely upon the experience of the preceding age of capitalism.  But what is to be done later, as conditions change more and more?  Of what use could the prices of 1900 be for the director in 1949?  And what use can the director in 1980 derive from the knowledge of the prices of 1949?

The paradox of "planning" is that is cannot plan, because of the absence of economic calculation.  What is called a planned economy is no economy at all.  It is just a system of groping about in the dark.  There is no question of a rational choice of means for the best possible attainment of the ultimate ends sought.  What is called conscious planning is precisely the elimination of conscious purposive action.

~ Ludwig von Mises, Human Action, pp. 700-701