In this book I have tried to develop further the ideas expressed in my previous work, Between Experience and Metaphysics, which was published in the same series in 1975. Several years have passed since the original Polish edition (and then 1 the Italian translation) of this book appeared. The fact that the principal ideas expressed in it have withstood, as I see it, the brunt of criticism, has led me to remain basically with the original text. Two main changes have, however, been introduced. First, I have added an Appendix containing the original version of a paper I presented at the...