The second son of a high government official, Constantijn Huygens received an all-round education before studying law at Leiden. As a diplomat he made several journeys abroad before being appointed (1625) private secretary of the stadholder, Frederick-Henry of Orange (1584–1647). He continued in this position under his son, William II (1626–50) and remained attached to the Orange family as an adviser on political, financial, and artistic questions. Huygens was a highly cultured and extremely versatile diplomat, poet, playwright, musician, and composer who spoke many languages, wrote hundreds of poems (in Dutch, Latin, and French), and took a keen interest in applied science. Huygens became interested in Descartes’ work after attending a demonstration by Descartes of his Dioptrics at Golius's home in 1632. After a personal meeting in Amsterdam in 1635, contacts intensified, and the two started a correspondence. Huygens encouraged Descartes to publish a few specimens of his early work and not deprive the world of his insights. Although Huygens had his hopes set on The World, which Descartes withheld to avoid alienating the church, these efforts eventually resulted in the publication of the Discourse on Method and accompanying essays (1637). He also supported Descartes in his efforts to realize the machine for grinding hyperbolic lenses described in the Dioptrics (AT VI 211–27) and commissioned a work on mechanics (Explication des engins, 1638). When he was not with the army, he dispatched Descartes’ mail safely and quickly via the Dutch embassy in Paris; he used his influence during Descartes’ conflicts with the Utrecht and Leiden universities; and on his behalf he mobilized his wide network. Although Descartes gratefully accepted all that, he politely but resolutely resisted Huygens's covert suggestions to become his official patron. That role would befall Princess Elisabeth and Queen Christina, two women clearly of a much higher social rank. In the eyes of Descartes, a nobleman, Huygens remained, much to the latter's frustration, a commoner after all.

See also Christina, Queen of Sweden; Discourse on Method; Dioptrics; Elisabeth, Princess of Bohemia; Huygens, Christiaan