The Scope of New Mechanism

New Mechanist Explanation (NME) has emerged as a leading contender for a general theory of scientific explanation, with proponents such as Glennan, Craver, and the MDC group arguing that mechanisms constitute the central unit of explanatory analysis across the sciences. This paper argues that NME's claim to generality is unsustainable. After reconstructing NME's core commitments and situating its development within the biotechnology boom of the late twentieth century, I identify a series of explanatory contexts in which NME fails: classical statics, dynamical and probabilistic models, field-theoretic explanation in classical electromagnetism, relativistic effects such as length contraction, and quantum phenomena including entanglement, indeterminacy, and tunneling. NME's own most sophisticated defenders concede that mechanisms "bottom out" in constraints and energetics — concessions which return mechanism to the physical and mathematical resources NME sought to displace. I conclude that NME is best understood as a regional theory of engineering and intervention sciences. The argument leaves open the question of what a genuinely general theory of scientific explanation should look like — a question I take up in subsequent work, where I propose a relational-structural alternative grounded in the indispensable role of mathematics in scientific reasoning.