  I present aspects of causal set theory (a research programme in quantum
gravity) as being en route to achieving a reduction of Lorentzian geometry to
causal sets. I take reduction in philosophers' sense; and I argue that the
prospects are good for there being a reduction of the type envisaged by Nagel.
(I also discuss the prospects for the stronger functionalist variant of
Nagelian reduction, that was formulated by Lewis.)
  One main theme will be causal set theory's use of a physical scale (viz. the
Planck scale) to formulate how it recovers a Lorentzian manifold. This use
illustrates various philosophical topics relevant to reduction, such as
limiting relations between theories, and the role of analogy. I also emphasise
causal set theory's probabilistic method, viz. Poisson sprinkling: which is
used both for formulating the reduction and for exploring its prospects.
