3. There is natural, violent, and local motion; rectilinear and circular motion Speed is proportional to motive force, and inversely proportional to resistance. F/R [by a constant of proportionality: v = k(F/R)] There cannot be a vacuum [therefore Natura is a plenum] The most Natural state: Rest [if terrestrial] Teleology - The 4th and Final Cause -- "WHY" is the most important question. [Aristotle's Theory of Causation ]