Supposing that the world is not a causal plenum, one might imagine that this or that cause does not have an infinite set of effects [alternatively: that the effect is not infinite] on the world. Thus Heisenberg’s uncertainty principle should not be applied to the exercise of each occasion of libertarian free will (or at least we should be suspicious of gratuitously granting that H.U. principle demonstrates that God must know ungrounded counterfactuals by middle knowledge in order to providentially order the world), since each may have a closed circle of causal influence on the world. In other words, my decision to do ‘x’ right now, may not have any causal relations whatever with Shin-yu in Japan making some other decision ‘y’ a few moments from now. Moreover, perhaps the ‘waves’ caused by my decision do eventually literally die off [are cancelled out] and have absolutely no causal influence on the decision of my child’s child. In order to imagine the latter one only need to imagine that the world isn’t a causal (and morally significant) plenum. If this were the case, then I wonder if God could providentially orchestrate the history of the world without having middle knowledge of molinist-type counterfactuals. This question is difficult to chew. If God knows that this or that decision is free, and thus only knows the fact of what decision I make (rather than the counterfactual) by means of scientia visionis, then perhaps God can, seeing [absent scientia visionis] what the causal sphere of influence decision ‘x’ will have either way, organize the conjunction of all decisions in such a way as to ensure that the world realizes the same grand (or eschatological) story. It is relatively easy to imagine that he could ensure the same basic grand story in a probabilistic sense, but can he do more than probably ensure it without knowledge of molinist-type counterfactuals if libertarian decisions have a limited scope of influence on the world? I’m not sure.
Interestingly, upon reflection, I think that the Catholic faith does implicitly entail that we accept that the world is a morally significant causal plenum (thus this will not be an acceptable way of rejecting ungrounded counterfactuals while accepting a strong view of providence). Perhaps the plenum also implies that decisions in the future can have some causal effect on states of affairs in the past – such as my choice now to not pray for ‘such-and-such’ person who has passed away. Our decisions each effect the world infinitely in petite ways which we cannot possibly perceive – even private sins or private acts of good, which do not apparently have any effect, are causally influential; they causally influence, in a morally significant way, all human beings present, future, and past. This is one of the reasons the response to the problem of evil typically given is a good one; that we are not at an epistemic vantage point to know whether this or that occasion of suffering had morally sufficient reason or else was gratuitous.
“There reigns among men, by the hidden and benign mystery of the divine will, a supernatural solidarity whereby the sin of one harms the others just as the holiness of one also benefits the others. Thus the Christian faithful give each other mutual aid to attain their supernatural aim… This is the very ancient dogma of the Communion of the Saints, whereby the life of each individual son of God in Christ and through Christ is joined by a wonderful link to the life of all his other Christian brothers in the supernatural unity of the Mystical Body of Christ till, as it were, a single mystical person is formed.”
 Indulgentarium Doctrina, Pope Paul VI