The only right method to be followed in philosophy is, undoubtedly, that which starts from facts; and to have proclaimed this method and rendered it universal is the merit of the modern school. On the other hand, passing over certain facts and building upon incomplete observations, are its continual defects. To know how to observe all the facts, to seize even upon those which most easily escape notice, as for instance those of our own spiritual feeling and consciousness, and then to accept impartially the legitimate consequences of the same, these are the qualifications of a true philosopher. To this end, a most vigilant and continual reflection upon oneself is necessary. That observation which is only able to take note of what happens externally to ourselves, of the impressions received by our corporeal senses from the action of matter, is observation of the grossest and most vulgar kind. It produces, not a mature philosophy, but a philosophy in the state of infancy. Such is the philosophy of Locke, of Condillac, of Destutt-Tracy, etc.
Antonio Rosmini, Theodicy, volume 1, Signini et al, tr., p. 139n.