Sentence:  The truth is that [Isaac] Newton was very much a product of his time. The colossus of science was not the first king of reason, Keynes wrote after reading Newton's unpublished manuscripts. Instead “he was the last of the <WSD>magicians</WSD>”. 
Meaning of the word marked with <WSD> tags:  A spiritualist or practitioner of mystic arts (often derogatory).