although different as regards their matter, are yet clearly moulded in the one form. This form is the intellect, the function of the brain. Descartes was probably the first who attained to the degree of reflection which this fundamental truth demands, and consequently he made it the starting-point of his philosophy, though provisionally only in the form of a sceptical doubt. When he took his _cogito ergo sum_ as alone certain, and provisionally regarded the existence of the world as problematical, he really discovered the essential and only right starting-point of all philosophy, and at the same time its _true_ foundation. This foundation is essentially and inevitably the _subjective_, the _individual consciousness_. For this alone is and remains immediate; everything else, whatever it may be, is mediated and conditioned through it, and is therefore dependent upon it. Therefore modern philosophy is rightly regarded as starting with Descartes, who was the father of it. Not long afterwards Berkeley followed the same path further, and attained to _idealism_ proper, _i.e._, to the knowledge that the world which is extended in space, thus the objective, material world in general, exists as such simply and solely in our _idea_, and that it is false, and indeed absurd, to attribute to it, _as such_, an existence apart from all idea and independent of the knowing subject, thus to assume matter as something absolute and possessed of real being in itself. But his correct and profound insight into this truth really constitutes Berkeley’s whole philosophy; in it he had exhausted himself.