Hexaemeron
The Hexaemeron interprets the Genesis with reference to Plato's "Timaeus". The text serves as a reasoned defense of God's existence, by relying on Platonic natural philosophy and Aristotelian logic to explain the creation of the world.[6] Thierry establishes that the moment of divine creation was the very beginning of time, and following that, creation evolved naturally through combinations of the four elements (fire, air, water, and earth).[7] According to Thierry, God created the four elements in the first moment. Fire, which is constantly moving, rotated and lit up the air, causing the first night and day. On the second day, fire warmed the water, causing it to rise into the heavens and form clouds. Because of the reduction of water, land emerged on the third day. The continued heating of the waters above the firmament caused the water to create the heavenly bodies on the fourth day. The continued warming of land caused the plant, animal, and human life to arise on the fifth and sixth days.
Thierry's explanation of the creation of the world is based on a theological interpretation of Aristotle's four causes, which he identifies with the three persons of the Trinity plus matter (made up of the four elements): the Father is the efficient cause, the Son is the formal cause, the Holy Spirit is the final cause and the four elements are the material cause.
According to Thierry, the act of divine creation is limited to the creation of the four elements, which then evolve by themselves, mix according to mathematical proportions and make up the physical world.
Heptateuch
The Heptateuch is a broad encyclopedia of information relating to the liberal arts, all within the context of academic and theologic unity. It particularly examines the ways in which different types of knowledge can be distinguished, while still supporting a single purpose: explaining order in reality. The trivium (logic, grammar, and rhetoric) address the veracity, consistency, and beauty of the language of expression. The quadrivium (geometry, astronomy, arithmetic, and music) provide the intellectual content in need of expression.
Thierry also wrote some commentaries on Boethius' De Trinitate.