J. VOLKELT, ERFAHRUNG UND DENKEN. 125

ledge. Every fact there is subjective in nature and individual. Absolute scepticism would thus be the necessary conclusion if there were not somehow given a kind of knowledge which, mak- ing no pretension to be objective, has the more valuable mark of absolute self -evidence. If there be such a knowledge, then on the basis of it something may be done for the theory of objective cog- nition. As was remarked, there is much resemblance in all this to the familiar Cartesian procedure ; and the answer offered strikes one immediately as little more than a modern setting of the cogito ergo sum, a setting which may be thought to bring to the front and exaggerate all that is unsatisfactory and dubious in the famous maxim. There is, Prof. Volkelt thinks, one knowledge possessed by us, in regard to which we enjoy absolute certainty, and are not exposed to the troublesome doubts roused by the notion of objec- tive cognition. " The slightest introspection shows me that I possess a knowledge (ein Wisseii) of the processes of my own con- sciousness." This knowledge is absolutely self-evident and indubi- table ; nay more, it carries with it the very principle of certainty. The fact of knowing my own mental states is in itself the evidence for the knowledge ; no further evidence is needed or is possible. It is to the credit of the book that, just at this point, which looks exquisitely simple and is really very complex, an attempt is made to explain in detail what is signified by the " knowledge " of one's own mental states. " In the first place there must be some processes in my consciousness ; secondly, my attention must have been directed upon them ; and thirdly, I must have been able to discriminate, fix and observe the processes which fall within the range of attention. Merely to have conscious pro- cesses is not identical with knowledge of them. . . . Nay, even the attentive treatment of contents of consciousness is not neces- sarily an absolutely certain knowledge ; it is further needful that I should be able to note their differences and limits " ; in brief, to observe them. Apparently too, we cannot allow ourselves to feel sure that we do know any mental state, until we are able to reproduce it with consciousness of its identity. Finally, Prof. Volkelt extends the range of subjective self-evidence, and includes within it not only the immediately observed facts of consciousness, but all the contents of memory. I must admit that, so far as I can understand the drift of this portion of the work, I entirely differ from the view apparently involved. It appears to me doubtful, even after Prof. Volkelt's careful statements, what exactly is meant by this knowledge and its certainty, and still more doubtful its connexion with the gene- ral problem of the work. Knowledge of inward states is here a process with its own contents ; the mental states as occurring hold to these contents the relation which the Cartesians described by the terms ease formaliter. I do not gather that Prof. Volkelt