Two Books, One Author

The book of nature is a longstanding Christian metaphor holding that God has revealed himself through two distinct books, scripture, God's revealed word, and nature, God's created work, and that because both books share the same divine author, rightly read they cannot ultimately contradict one another, a principle that gave many pre-modern and early modern Christian thinkers grounds for pursuing natural philosophy, the historical ancestor of modern science, as a genuinely religious as well as intellectual undertaking. The metaphor has roots reaching back to patristic writers including Augustine, who described creation itself as a kind of book available to be read even by the illiterate, and it received one of its most consequential applications when Galileo Galilei invoked the two books principle directly in his 1615 Letter to the Grand Duchess Christina, arguing that apparent conflicts between the literal text of scripture and the findings of natural philosophy should be resolved by recognizing that scripture is written to accommodate ordinary human understanding on matters of salvation, while nature, correctly investigated, speaks with its own unmediated and equally divine authority on matters of physical fact.