A philosophical archive for the constructive study of substance dualism: www.newdualism.org.
The fundamental idea for 'Generative Dualism' is that, where there are two discrete degrees 'mind' and 'body':
In the language of causation:
The events in the body depend on the propensities there, and also on the events in the corresponding positions in the mental degree. What goals and propensities are present depend on the past actualities/outcomes.
There is thus an appearance of bi-directional interaction between all degrees, but this is always based on a principle of Conditional Forward Production:
The processes at any stage are again the joint production of `Principal Causation' from the preceding propensities, and of `Instrumental Causation' from which effects are already actual. Only in the instrumental sense can events ever said to be causally efficacious.
Are minds and bodies separate substances, on this account?
Yes: they are two substances which may be distinguished from each other, though the activity in the body always depends on dispositions in the mind, and though the perpetuation of definite mental forms depends on past activities of the body.
If we take substances to be defined as propensities in particular forms, then mind and body are indeed distinct substances.
The mind and body are not homogeneously continuous with other: not continuously transformable one into another. Rather, they are 'contiguous' with each other: where the mind ends its action is where the body begins its new propensities.