"All Is Leaf": Difference, Metamorphosis, And Goethe's Phenomenology of Knowledge (Critical Essay‪)‬

All things created would seem, in a way, to be purposeless, if they lacked an operation proper to them; since the purpose of everything is its operation [Omnes res creatae viderentur quodammodo esse frustra, si propria operatione destituerentur, cum omnis res sit propter suam operationem]. --St. Thomas Aquinas