George Sinclair

George Sinclair was a Scottish mathematician, engineer, and minister who died in 1696. He is generally identified as the first Professor of Mathematics at the University of Glasgow, and he wrote on subjects that now seem strikingly far apart: mathematics, mining and engineering, hydrostatics, and reports of spirits and witchcraft.

His best-known book is Satan's Invisible World Discovered from the 1680s, a collection of stories and testimony about apparitions, demons, and witches. That work helped preserve some of the most famous supernatural tales in Scottish tradition, including the "Glenluce Devil" case, and it has kept his name in print long after his technical writing became more specialized.

What makes Sinclair memorable is that he reflects a time when natural philosophy, religion, and the study of unusual phenomena were not neatly separated. In his work, practical science and belief in the invisible world sit side by side, giving modern readers a vivid glimpse of how people in 17th-century Scotland tried to understand both the physical world and the unexplained.