A t the end of Chapter V III we said that the Critical Scientific Theory of physical objects and our perception of them left two main problems on hand. One was to clear up the meanings of physical place, shape, size, date, duration, etc., and to establish their cash value in terms of those corresponding characteristics of our sensa, on which they must ultimately be founded. This task I have performed to the best of my ability in the last four chapters. The other problem was to elucidate the very obscure statement that external physical objects and our own bodies “ jointly produce in us the sensa by which these external bodies appear to us.” Probably any solution of this problem will be found to favour (if not actually to require) some particular view as to the nature of sensa and their ontological status in the universe. So this book will fitly end with an attempt to define the meaning and estimate the truth of the above statement.