Full Idea
Armstrong's combinatorial theory of possibility is perhaps the most sophisticated and best worked out reductionist version of actualism to date.
Gist of Idea
The best version of reductionist actualism around is Armstrong's combinatorial account
Source
report of David M. Armstrong (The Nature of Possibility [1986]) by Stephen Read - Thinking About Logic Ch.4
Book Reference
Read,Stephen: 'Thinking About Logic' [OUP 1995], p.118