Three principles of unity in Newton

I discuss three principles of unity available in Newton’s physics, appealing to space and time, causal interaction, and law-constitution respectively. I compare these three approaches with respect to aggregation (how a collection of entities can compose a whole) and multiplicity (how the world as a whole can contain a multiplicity of genuine unities), outlining the problems faced by the first two approaches and arguing that the third looks a promising candidate for further philosophical investigation.