The Gregorys were Jacobites and left Scotland to escape religious discrimination.

Young David visited several countries on the continent, including the Netherlands (where he began studying medicine at Leiden University) and France, and did not return to Scotland until 1683.

He was "the first to openly teach the doctrines of the Principia, in a public seminary...in those days this was a daring innovation.

"[2] Gregory decided to leave for England where, in 1691, he was elected Savilian Professor of Astronomy at the University of Oxford, due in large part to the influence of Isaac Newton.

[3] In 1695 he published Catoptricae et dioptricae sphaericae elementa which addressed chromatic aberration and the possibility of its correction with achromatic lens.