  We introduce a generalization of team semantics which provides a framework
for manipulationist theories of causation based on structural equation models,
such as Woodward's and Pearl's; our causal teams incorporate (partial or total)
information about functional dependencies that are invariant under
interventions. We give a unified treatment of observational and causal aspects
of causal models by isolating two operators on causal teams which correspond,
respectively, to conditioning and to interventionist counterfactual
implication.
  The evaluation of counterfactuals may involve the production of partially
determined teams. We suggest a way of dealing with such cases by 1) the
introduction of formal entries in causal teams, and 2) the introduction of
weaker truth values (falsifiability and admissibility), for which we suggest
some plausible semantical clauses.
  We introduce formal languages for both deterministic and probabilistic causal
discourse, and study in some detail their inferential aspects. Finally, we
apply our framework to the analysis of direct and total causation, and other
notions of dependence and invariance.
