Walter Warner was born in Leicestershire and died in London. He was educated at Merton College, Oxford and received his BA on 28 June 1578. Along with Thomas Harriot, Robert Hues and Nathaniel Torperley, Warner was a pensioner of Henry Percy, ninth Earl of Northumberland, a patron of mathematicians and natural philosophers, and received an annuity of £60 per year. Warner had particular responsibilities for the earl's library, arranging for transportation of books to and from Syon House while Percy was imprisoned in the Tower from 1605 to 1621. He also accompanied Percy on his military expeditions to the Low Countries in 1600–1601. After Percy's death in 1632, for a brief time he continued to receive a pension from the tenth earl, Algernon Percy. He then sought and gained the support of Sir Thomas Aylesbury. In the early 1630s he also sought the patronage of William Cavendish, Earl of Newcastle and his brother Charles, from whom he received £20 in 1635 for sending two tracts, one on the construction of telescopes, and another on the location of images in convex and concave glasses (De loco imaginis). Warner engaged in a correspondence in connection with the latter treatise with Robert Payne and Thomas Hobbes, who both offered serious criticisms of his work. According to Izaak Walton, Warner spent most of the latter part of his life in Woolstable near Charing Cross, spending his summers with Aylesbury at Windsor Park.
From The Continuum Encyclopedia of British Philosophy in Oxford Reference.