What is the Fourth Dimension? (1884)
An 1884 essay explores the concept of a fourth spatial dimension using analogies like Flatland to explain how a higher-dimensional being might interact with our three-dimensional world.
Background
Charles Hinton was a British mathematician and science fiction writer whose 1884 essay popularised the idea of a fourth spatial dimension as a way to visualise higher geometry. Written for the general reader, the essay uses simple analogies — like how a flatland creature would perceive a three-dimensional object — to explain how a 4D being might see our world. The essay predates Einstein's relativistic spacetime (1905) by two decades, imagining the fourth dimension as purely spatial, not temporal. Hinton later coined the word "tesseract" for the 4D cube. The piece is a landmark in the popularisation of non-Euclidean geometry and influenced later authors like H.G. Wells and Jorge Luis Borges.