Andreas Libavius' (c. 1555-1616) three part collection of letters, the "Rerum chymicarum epistolica forma...liber" (1595-1599) is a particularly important text in fashioning the subject of chemistry as a demonstrative science and as a didactic discipline. Where Libavius' "Alchemia", which some have claimed to be the first textbook of chemistry, had mostly a humanist agenda, the "Rerum chymicarum...liber" more directly sought to wrest the subject of "chemistry" away from Paracelsian adepts, and established the methodological basis for a specific form of knowledge suitable to the university. Making use of Aristotle's "Posterior analytics" Libavius created a "floor-plan" for chemistry that integrated practical experience with natural philosophy, and could thus, he claimed, penetrate more deeply into the structure of nature than other academic disciplines.