John Craig was the son of an Edinburgh merchant related to the Craigs of Craigfintray, Aberdeenshire. His father is said to have continued Catholic after the Reformation, so after taking an initial degree in arts at St Mary's College, St Andrews in 1567, the young John probably studied briefly in France. Converting to Protestantism, he proceeded to Königsberg, where he arrived in 1569. The following year he moved to Wittenberg, where he studied medicine under Caspar Peucer; then in 1573 he is found at Frankfurt-on-Oder as Professor of Mathematics and Logic. His lectures there of 1581 were on Melanchthon's Aristotelian-based logic. His eldest brother, Thomas, the legal theorist, acquired Craigfintray in 1576. John returned to Scotland in 1584. In 1601 he became heir to his younger brother James, merchant and Scots agent in Bordeaux.
From The Continuum Encyclopedia of British Philosophy in Oxford Reference.