Of course, theory becomes purposeless if it is not connected with revolutionary practice, just as practice gropes in the dark if its path is not illumined by revolutionary theory.

Lenin and Mao agree with Stalin:

"Without revolutionary theory, there can be no revolutionary movement, " —Lenin

“No political party can possibly lead a great revolutionary movement to victory unless it possesses revolutionary theory and a knowledge of history and has a profound grasp of the practical movement.” —Mao

And:

“If we have a correct theory but merely prate about it, pigeonhole it and do not put it into practice, then that theory, however good, is of no significance.” —Mao