Johann Georg Hamann (August 27, 1730, Königsberg – June 21, 1788, Münster) was an important German philosopher, a main proponent of the Sturm und Drang movement, and associated by historian of ideas Isaiah Berlin with the Counter-Enlightenment. He was Pietist Lutheran, and a friend (while being an intellectual opponent) of the philosopher Immanuel Kant. He was also a lutenist, having studied this instrument with Timofey Belogradsky (a student of Sylvius Leopold Weiss), a Ukrainian virtuoso then living in Königsberg. He was known by the epithet Magus im Norden ("Magus of the North").
His distrust of reason and the Enlightenment ("I look upon logical proofs the way a well-bred girl looks upon a love letter" was one of his many witicisms) led him to conclude that faith in God was the only solution to the vexing problems of philosophy.
Johann Georg Hamann might be one of the most influential writers you've never heard of. A friend and intellectual sparring partner of Kant's, Hamann was the first vocal critic of Kant's new philosophical system, and a radical and outspoken opponent of the Enlightenment in general. Goethe was a huge fan, and Kierkegaard would later quote Hamann (a Christian, although of a kind that one doesn't come across much today) and look to him for spiritual inspiration.
Part of his obscurity is due to the fact that his works are deeply allusive and unabashedly esoteric. (The subtitle of "Aesthetica in nuce" would be translated as "A rhapsody in Kabbalistic prose.") His "philosophy," if you can call it that, brings to mind some of the main undercurrents of continental philosophy in the 20th Century: he was a vocal advocate of moral and cultural historicism and relativism; privileged poetry and history over rationality and natural science; thought of the entire universe, natural and written, as a code, a language, a system of signs (written by God) to be deciphered; and was deeply opposed to a bourgeois, capitalist work ethic (the incription of "Socratic memorabilia" reads "for the boredom of the public compiled by a lover of boredom") and the rationalization of society. His stock has been rising in recent years, at least in Germany; I'd love to see the same thing happen in the English-speaking world.
This edition has excellent, extensive, and much-needed side-notes: each page of text is faced by a page of notes, which is absolutely necessary for those who, like me, are not masters of Latin, Ancient Greek, Classical Hebrew, or French, and haven't memorized the entirety of the Bible. There's also an extensive afterword. Highly recommended.