The basic idea of interventionist theories of causation is this: X causes Y iff there is a possible intervention on X for Y, and if the value of X were changed as a result of that intervention, then the value of Y would change. These theories are subdivided into reductive and non-reductive accounts. Reductive accounts, advanced by Menzies and Price (1993), reduce the notion of causation to a non-causal notion of intervention, while according to non-reductive accounts advanced by Woodward (2003), such a reduction is not possible. In the present paper, I investigate causation in algebraic quantum field theory from Woodward's point of view. I define the necessary condition for no causal relationship between the local algebras associated with two spacelike separated region, and show that this condition always holds under the usual axioms of algebraic quantum field theory.
