The Riddles of Philosophy by Rudolf Steiner. Volume 18 in the collected works (CW).
[Due to the considerable length of this work I will be posting the sections as each is completed, instead of all at once.] Also, I have rearranged the files a bit for those of you who have been downloading these as they come (2 has been put together into 1 file and I have renamed the rest to correspond with the chapters).
1. Chapter 1: Guiding Thoughts on the Method of Presentation
2. Chapter 2: The World Conception of the Greek Thinkers
3. Chapter 3: Thought Life from the Beginning of the Christian Era to John Scotus Erigena
4. Chapter 4: The World Conceptions of the Middle Ages
5. Chapter 5: The World Conceptions of the Modern Age of Thought Evolution