“Truth was no longer to be ascertained by consulting authority, but by inward meditation. There was a tendency, quickly developed, towards anarchism in politics, and, in religion, towards mysticism (…) The result, in thought as in literature, was a continually deepening subjectivism, operating at first as a wholesome liberation from spiritual slavery, but advancing steadily towards a personal isolation inimical to social sanity.
Modern philosophy begins with Descartes, whose fundamental certainty is the existence of himself and his thoughts, from which the external world is to be inferred. This was only the first stage in a development, through Berkeley and Kant, to Fichte, for whom everything is only an emanation of the ego. This was insanity, and, from this extreme, philosophy has been attempting, ever since, to escape into the world of everyday common sense.”Russell, Bertrand – History of Western Philosophy