We can learn more about metaphysical realism and about how it can best be supported by looking at Castañeda's excursions into metaphysics in part II of his Self-profile (1984) and in his 1988 paper, "Metaphysical Internalism, Selves and the Indivisible Noumenon." In particular we can reach the following conclusions. Metaphysical realism is somehow delivered by the Cartesian Cogito, which certifies with metaphysical certainty that there are objects, properties, relations and states of affairs. In contrast to what Castañeda claims, this makes it difficult to say that reality in itself must be conceived of simply as an "ineffable undifferentiated whole." And it also opens the way, abductively, for common sense and scientific realism. But, following Castañeda, we must admit that we have different levels of knowledge and certainty and that this abductive knowledge does not grant absolute metaphysical certainty for the deliverances of common sense and scientific realism.