To provide metaphysical grounds for the physics of her time, Du Châtelet argued for the notion of an active force. This was different from the impressed force in Newton’s second law. The former force was a property of a body, whereas the latter was an external cause. I shall study this discrepancy and argue that the interactive concept of force in Newton’s third law is consistent with Du Châtelet’s standards for an intelligible physics. Consequently, the interaction entailed by the law (...) of universal gravitation complies with Du Châtelet’s principles of human knowledge. (shrink)

My thesis in this paper is: the modern concept of laws of motion—qua dynamical laws—emerges in 18th-century mechanics. The driving factor for it was the need to extend mechanics beyond the centroid theories of the late-1600s. The enabling result behind it was the rise of differential equations. -/- In consequence, by the mid-1700s we see a deep shift in the form and status of laws of motion. The shift is among the critical inflection points where early modern mechanics turns into (...) classical mechanics as we know it. Previously, laws of motion had been channels for truth and reference into mechanics. By 1750, the laws lose these features. Instead, now they just assert equalities between functions; and serve just to entail (differential) equations of motion for particular mechanical setups. This creates two philosophical problems. First, it’s unclear what counts as evidence for the laws of motion in the Enlightenment. Second, it’s a mystery whether these laws retain any notion of causality. That subverts the early-modern dictum that physics is a science of causes. (shrink)