This work approaches Spinoza's work, focusing on the place that the notion of freedom of expression occupies in it. Much of the work of this philosopher is an exhibition of arguments to defend the democratic regime - and, even more, the democratic way of life - understood by the author as the best regime to be, among all possible forms, the more natural, that which comes closest to the ultimate objective of the State. In this context, the defense of Spinoza's freedom of expression is, in the end, a defense of democracy. In relation to the above, according to this author, freedom of expression (the defense of which is inseparable from the defense of Reason) is the condition of possibility of Democracy because it is only with freedom of expression that the rationality of decisions is guaranteed and, consequently, the gradual increase in the efficiency of the democratic system.