Hello again,
Thanks for your helpful remarks. I still seem to be having some problems grasping your framework, however; I'll try to explain as best I can.
Your statement that selection determines effect seems to imply that selection is sufficient to produce an observable effect. Yet the selection of two open slits does not, by itself, produce an effect; it's also necessary to have a detection screen. Hence, selection here is not deterministic.
Of course, one can always say that selection in this case does determine something, namely that there are two different possible effects; but your own reference to "effects observed on the detection screen" suggests you're talking about actual, observed effects rather than possible ones. In any case, no one denies that selecting a particular experimental set-up determines a range of possible effects; what's at issue is whether actual effects or outcomes are causally determined.
Regarding spin and helicity, you say on p. 5 that "acts of selection are causal and when combined with their effectual states on the corresponding selection axis create a state of angular momentum." One difficulty I have here is that I can't think of any examples at all of "direct" selection of spin states. But more importantly, you don't seem to offer any specific, physical account of how the above-mentioned process of spin-state-creation actually works. Of course, we already know how spin can be measured using, e.g., a Stern-Gerlach apparatus. But you seem to be offering an alternative to standard accounts of (spin-)measurement; and I just can't tell what that alternative is.
I apologize, again, if I'm missing something.
-Willard