Candidates for fundamental physical laws rarely, if ever, employ higher than second time derivatives. Easwaran ([2014]) sketches an enticing story that purports to explain away this puzzling fact and thereby provides indirect evidence for a particular set of metaphysical theses used in the explanation. I object to both the scope and coherence of Easwaran’s account, before going on to defend an alternative, more metaphysically deflationary explanation: in interacting Lagrangian field theories, it is either impossible or very hard to incorporate higher than second time derivatives without rendering the vacuum state unstable. The so-called Ostrogradski instability represents a powerful constraint on the construction of new field theories and supplies a novel, largely overlooked example of non-causal explanation in physics.

1.  Introduction: Why Does F = ma?

2.  Easwaran's Metaphysical Explanation

3.  The Ostrogradksi Theorem

4.  A Physical Explanation

5.  Laws, Meta-laws, and Non-causal Explanation