In a letter
of October or November, 1674, Spinoza writes:

Thus, I call a thing free that exists and acts out
of the pure necessity of its nature; and I call it compelled, if its existence and activity are determined
in a precise and fixed manner by something else.
Thus God, for example, though necessary, is free,
because he exists only out of the necessity of his
nature. Similarly, God knows himself and everything else freely, because it follows from the necessity of his nature alone that he should know
everything. You see, then, that I locate freedom not
in free decision, but in free necessity.
Let us, however, descend to created things,
which are all determined to exist and to act in fixed
and precise ways by outside causes. To see this
more clearly, let us imagine a very simple case. A
stone, for example, receives a certain momentum
from an external cause that comes into contact with
it, so that later, when the impact of the external
cause has ceased, it necessarily continues to move.
This persistence of the stone is compelled, and not
necessary, because it had to be established by the
impact of an external cause. What applies here to
the stone, applies to everything else, no matter how
complex and multifaceted; everything is necessarily determined by an outside cause to exist and to
act in a fixed and precise manner.
Now please assume that the stone, as it moves,
thinks and knows that it is trying, as much as it
can, to continue in motion. This stone, which is
only conscious of its effort and by no means indifferent, will believe that it is quite free and that it
continues in its motion not because of an external
cause but only because it wills to do so. But this is
that human freedom that all claim to possess and
that only consists in people being aware of their
desires, but not knowing the causes by which they
are determined. Thus the child believes that it
freely desires the milk; the angry boy, that he freely
demands revenge; and the coward flight. Again,
drunkards believe it is a free decision to say what,
when sober again, they will wish that they had not
said, and since this prejudice is inborn in all
humans, it is not easy to free oneself from it. For,
although experience teaches us sufficiently that
people are least able to moderate their desires and
that, moved by contradictory passions, they see
what is better and do what is worse, yet they still
consider themselves free, and this because they
desire some things less intensely and because some
desires can be easily inhibited through the recollection of something else that is familiar.

Because this view is expressed clearly and definitely, it
is easy to discover the fundamental error in it. Just as a
stone necessarily carries out a specific movement in response to an impact, human beings are supposed to carry
out an action by a similar necessity if impelled to it by any
reason. Human beings imagine themselves to be the free
originators of their actions only because they are aware of
these actions. In so doing, however, they overlook the
causes driving them, which they must obey unerringly.
The error in this train of thought is easy to find. Spinoza
and all who think like him overlook the human capacity
to be aware not only of one’s actions, but also of the causes by which one’s actions are guided.

A Philosophy of Freedom - Rudolf Steiner