What does Orwell mean by the statement "Freedom is the freedom to say that two plus two make four. If that is granted, all else follows."

George Orwell, in his 1946 essay, "Politics
and the English Language", argues for an inherent connection between
political freedom and clear language. In many ways, Orwell's ideas derive from John
Stuart Mill's essay "On Liberty`which argues that the most important form of liberty is
free speech, because it is only in an open marketplace of ideas, where viewpoints are
questioned and tested against one another that truth can emerge. Improvements in
society, whether political, ethical, or commerical all depend on the ability of citizens
to put forth new ideas and discuss them openly; where there is no free speech, there is
only stagnation and tyranny. Orwell adds to Mills concept of free speech the addition of
clear speech. In an era with increasing power of mass media, Orwell sees that the
putative freedom of speech possessed by citizens in mass culture was illusory of part of
the debate was framed in speech so unclear that the fundamental mechanisms of liberty,
those of open debate, were undermined by language so obfuscatory that those in control
of the media could constantly reframe the grounds of debate to reinforce their own
power, as do the rulers in 1984. Mass communication  shifts the locus of power in the
novel to those who control the means of communication.