That I have ideas is in the same sense matter of observation to me as that other objects have colour, sound, etc. I am now also able to distinguish these other objects, which stand over against me, by the name of the outer world, whereas the contents of my perception of my Self form my inner world. The failure to recognise the true relation between idea and object has led to the greatest misunderstandings in modern philosophy. The fact that I perceive a change in myself, that my Self undergoes a modification, has been thrust into the foreground, whilst the object which causes these modifications is altogether ignored. In consequence it has been said that we perceive, not objects, but only our ideas. I know, so it is said, nothing of the table in itself, which is the object of my perception, but only of the changes which occur within me when I perceive a table. This theory should not be confused with the Berkeleyan theory mentioned above. Berkeley maintains the subjective nature of my perceptual contents, but he does not say that I can know only my own ideas. He limits my knowledge to my ideas because, on his view, there are no objects other than ideas. What I perceive as a table no longer exists, according to Berkeley, when I cease to look at it. This is why Berkeley holds that our percepts are created directly by the omnipotence of God. I see a table because God causes this percept in me. For Berkeley, therefore, nothing is real except God and human spirits. What we call the "world" exists only in spirits. What the naïve man calls the outer world, or material nature, is for Berkeley non-existent. This theory is confronted by the now predominant Kantian view which limits our knowledge of the world to our ideas, not because of any conviction that nothing beyond these ideas exists, but because it holds that we are so organised that we can have knowledge only of the changes within our own selves, not of the things-in-themselves which are the causes of these changes. This view concludes from the fact that I know only my own ideas, not that there is no reality independent of them, but only that the subject cannot have direct knowledge of such reality. The mind can merely "through the medium of its subjective thoughts imagine it, conceive it, know it, or perhaps also fail to know it" (O. Liebmann, Zur Analysis der Wirklichkeit, p. 28). Kantians believe that their principles are absolutely certain, indeed immediately evident, without any proof. "The most fundamental principle which the philosopher must begin by grasping clearly, consists in the recognition that our knowledge, in the first instance, does not extend beyond our ideas. Our ideas are all that we immediately have and experience, and just because we have immediate experience of them the most radical doubt cannot rob us of this knowledge. On the other hand, the knowledge which transcends my ideas--taking ideas here in the widest possible sense, so as to include all psychical