The aim of Athanasius Kircher's scientific investigations is precise: to find the truth of the world. According to the authoritative theological conception of his time, God would have hidden this truth in nature. Therfore, Kircher searches for and tries to decipher the clues leading, or so he believes, to this buried original knowledge. According to him, deciphering the code of this language will lead to the truth given by God to Adam, so that he can pass it on to humanity.

Following this theological-mystical conception, Athanasius will try, throughout his life, to unravel the mysteries of nature and human languages. A keen observer, he risks his own life to observe himself the objects of his study: travel to distant lands, exploration of volcanoes…

Studying volcanoes gave Athanase Kircher the idea of writing a treatise entirely dedicated to the world beneath the surface of the earth, the famous Mundus subterraneus.

However, Kircher did not stop there, because his thirst for knowledge was universal. His explorations were also intellectual: building on the work of great philosophers, he developed his own theories and thought patterns.

The reproduction below shows Kircher's version of the tree of Porphyry (234-310), a neo-platonic philosopher, which slices reality according to Plato's definitional method: by division.

Where Ramon LLull proposed his Arbor Moralis and Arbor Scientiae, Athanasius Kircher re-used the ontological structure of Porphyry to classify « all that is ». Where the tree usually stops – the primal essence, "this man, Plato, etc." - Kircher added one level, belonging to Jesus Christ (insofar as he is a man) and connecting contradictory properties (temporal and eternal…). Above Jesus Christ (as the son of the Eternal Father) sits the Trinity symbolized by a triangle with an eye in the center. The Trinity radiates various categories, including the eighteen organizing principles (nine divine / absolute principles and nine logical / relative principles) of Llull's thought (Arbor Scientiae).