We summarize these remarks as follows: The proposition system of a classical system is a lattice with a distinguished orthocomplementation operation: The lattice operations of meet and join are respectively set intersection and set union. The orthocomplementation operation is set complement. Moreover, this lattice is sequentially complete, in the sense that any sequence { E i } i ∈ N of elements of the lattice has a least upper bound, specifically the set-theoretic union: LUB ⁡ ⁡ ( { E i } ) = ⋃ ⋃ i = 1 ∞ ∞ E i .