Every culture has its own “world of knowledge”, a way in which it conceives the limits of human knowledge: what one knows, what one can know, and what one cannot know. This study seeks to explore the Ottoman “world of knowledge” and its historical development: the way the horizons of this mental universe were delineated in space and time; the way these horizons expanded (or contracted) over time; the way this universe was seen as having limits, showing fields that could not (or should not) be known and how these limits shifted to and fro in the continuum of reality; and, finally, the way knowledge was organized, i.e. taxonomies of the fields of science, demonstrating hierarchies of the world in relation to what was deemed necessary, useful, or harmful to man.