In this paper, I want to show how counterfactual history (a branch of history exploring what would have happened if things had been different) needs the denial of CCP (Causal Closure of the Physical). This essay is merely for the counterfactual historian who wants to explore possibilities in the context of history and who accepts that “although some HE (historical event) occurred, if HE had not occurred, then HE* would have resulted.” If my conclusion is correct, it is fascinating that an entire form of history requires this heavy of a presupposition. As such, I will explain what CCP is and explain why, for two reasons, counterfactual history should deny it. Secondly, if my argument is correct, I will show one implication of my view, namely, philosophical arguments generally should not be taken to be plausibly false if they rest on a controversial premise.
CCP is the view that reality is a system of inter-locked events with the implication of causal determinism . Broadly, what happens i.e., HE, happens necessarily. For instance, suppose that
(1) Hitler died April 30, 1945
is a true proposition. If CCP is true, (1) is necessarily true (it is not possible for Hitler to have died any other time than 1945). But, if (1) could not have been different than it is, it follows that all history is the inevitable consequence of causally determined laws which preclude any form of possibility beyond what the laws allow. Not only would this imply that counterfactual history is mere make-believe (since any ‘if-then’ other than what happens in the actual world cannot happen in principle), but it rids history of any moral significance (taking the assumption that on determinism (with respect to persons) entails not having moral responsibility). So, my view is that the counterfactual historian should deny CCP for two reasons: (i) history, on CCP, is without moral significance and (ii) without denying CCP, any counterfactual (if P were the case, then Q) is a working of the imagination—there are no counterfactuals which are true in other possible worlds (unless they were exactly like the actual world—in which case one would be talking about the actual, not possible world—which is just describing our world).
One could argue against this and say that although CCP is true, it is possible that there could have been a different world than ours which was actualized (and thus the actual world can have necessarily occurring events while remaining open to counterfactual possibilities). To this I would respond that although this might pose a problem for the person who wants to deny any other counterfactuals than the ones of the actual world, my argument simply says that in the actual world the counterfactual historian is interested in some historical event being different in virtue prior conditions and not in some other possible world (the counterfactual historian wants to know whether nor not in the actual world things could have been different). Here is an example. Suppose that a historian Prof. Lydia, wants to inquire whether (1) could have been different and so
(2) Hitler died on December 1, 1946
would be (possibly) true. This would be irrelevant if (2) was only true in another possible world. Presumably if the historian wants to accept that things could have been different, it is for a reason which is relevant to this world and not another possible world. So, if one wanted to know whether or not WW2 could have been prevented, it is not significant whether or not in some other possible world this is true (inasmuch as the other possible worlds are unactual)—it is in the actual world that it matters.
If my thesis is correct, there exists sufficient motivation for the counterfactual historian to reject CCP and to accept any framework i.e., an indeterministic one, which does not preclude counterfactuals describing the actual world. While philosophically denying CCP is a heavy presupposition for an entire discipline, denying CCP is epistemologically favorable given that counterfactual history gives (minimally) possible true conclusions i.e., if Hitler had not existed, WW2 would not have happened, or something like that and moral significance to history (we can learn from history i.e., WW2 and change the future i.e., prevent something like WW2 from happening).
 I take CCP to entail causal determinism for one reason, namely, that if every event has a physical antecedent cause, it does not seem possible for any freedom to come into the picture. (Perhaps the CCP I am assuming here also includes physicalism). If causal determinism is true (and precludes any freedom), then it would follow that no event in the history of events could have been different in the actual world.