Force and dynamism (actuality and potentiality; energeíta and dunámis) together constitute one of the four fundamental “ways” of being described by Aristotle in the Metaphysics; and one of the two “ways,” along with being according to the categories, that constitutes the subject matter of the primary science. Aristotle’s ontology remains the phenomenologist’s touchstone, and indeed this characterization of being has guided the work of Heidegger among others.