This study concerns the late Renaissance metaphysics of light in its adoption to a Paracelsian alchemical context by John Dee, Heinrich Khunrath, Michael Maier and Robert Fludd. Their alchemical theosophy is contextualised within Protestant reformism of the 1590s to 1620s, specifically that of Valentin Weigel and Johannes Arndt. This results in a re-assessment of the Rosicrucian movement which challenges the existing historiography and problematises the character of the movement. The volume includes fifty illustrations from alchemical treatises of the period, the emphasis being placed on Khunrath's "Amphiteatrum Sapientiae Aeternae (1595-1609). In an innovative manner, the study investigates these images using analytical tools drawn from semiotics, structuralism and post-structuralism. This method yields an unusual interpretation of the geometry, optical diagrams and spatial structures employed in such alchemical engravings.