 Kuhn does insist that Helmholtz formulated the principle. Robert Purrington observes, following Kuhn, that “There was a widely held, intuitive view that the total quantity of force (or motion) might be somehow constant, but it did not necessarily imply an ability to distinguish the vector nature of force or momentum from the scalar energy” (Purrington 1997, 105). In his “Philosophical Introduction” to the essay, Helmholtz himself argues that his task in the essay is not to find new experimental evidence or a completely new principle, but rather to explain the “unknown causes” of the phenomena from their “visible actions” according to the “laws of causality”: 