In a letter written to Herder in July 1772, Goethe reports:

This letter attests to Goethe's wide-ranging and eclectic approach to classical sources. Ernst Grumach's two volume collection of Goethe's reflections on the ancients — Goethe und die Antike (Goethe and Antiquity, 1949) — demonstrates that Goethe's interest in the classical world ranged from poetry, drama, mythology, and philosophy to architecture, painting, sculpture, rhetoric, and law. For this reason, the question as to precisely which classical sources exerted the most influence upon Goethe is difficult to answer, and responses to this problem have accordingly led to broad, synoptic studies like Ernst Maass's Goethe und die Antike (Goethe and Antiquity, 1912, not to be confused with Grumach's later collection) and Humphry Trevelyan's Goethe and the Greeks (1941).

When we turn to the question of the influence exerted by classical philosophy upon Goethe's thought, the picture becomes slightly clearer. We know that Goethe was familiar with and read parts of Johann Jakob Brucker's multi-volume Historica critica philosophiae (Critical History of Philosophy, 1766–67) during his youth, volumes one and two of which provide the reader with a broad overview of classical thought from the pre-Socratics, via Socrates and Plato, to Aristotle, Stoicism, and Neo-Platonism.