If you don’t already know, I’m a hard incompatibilist. This means I think free will is logically incoherent in both a deterministic universe as well as an indeterministic universe. In this post, I just want to address if the universe is a “deterministic universe”, meaning entirely causal (all events have a cause), and what such would mean for the word “possibility”.
There are different branches of philosophy. One of these branches is called “epistemology” which is the branch that is concerned with the nature of knowledge. In other words, what we can know, how we can know it, and so on. Another is called “ontology” which is the branch that is concerned with existence (or “being”, “becoming”, “reality”). In other words, it addresses what exists, how it exists, if something cannot exist, and so on.
These two branches are more often conflated than not. People address epistemology when they should be addressing ontology, or ontology for epistemological usages of words. This is very problematic and causes great confusion.
To give an example of how these are used, the claim “rocks exist in the box” is an ontological claim. The claim that “a heavy box is probably filled with rocks” is epistemological. We may not know (epistemology) that the box is filled with rocks, but either they do exist (ontology) in the box or they do not.
Without knowing which is the case, we might say it’s possible that the box is filled with rocks but it’s also possible that the box is not filled with rocks. To our knowledge both of these are “possible”.
But our “knowledge” and what is “actual” (in a deterministic universe) are two very different things. Ontologically, it’s the case that it is not possible that the rocks both exist in the box and don’t exist in the box. If the box happens to be filled with rocks, it was never the case that it “could have” not been filled with rocks (e.g. have been filled with water instead).
In a deterministic universe, we say that someone couldn’t have chosen otherwise. That any other perceived “possibility” at the time weren’t real “possibilities” at all. They were firmly in the realm of epistemological possibilities, not “real” ontological possibilities.
To understand the distinction lets do so from the point of view of two people. Person A doesn’t know what is in the box. Person B, however, knows that the box is filled with peanut butter.
For person A, it is possible that the box is filled with rocks. For person B, however, who knows what’s in the box, it’s not possible that the box is filled with rocks. It can only be filled with peanut butter. These two different perspectives point out where the word “possibility” is, at least for the case of what’s in the box. And it’s entirely in the realm of knowledge. The one who doesn’t know what’s in the box can imagine a number of different “possibilities” for what’s in the box. But in reality, only one of those were ever “real” possibilities (if one of the possibilities imagined was peanut butter).
When people say that the options they have in front of them (before they select one) are all causally possible, they are talking in the same usage as the above. They don’t know all of the variables until they play out, so they attach the word “possible” to the options they don’t know will happen or not. This is fine in the epistemological sense, but in the ontological sense it just isn’t the case. Yet many people will think it is the case that these possibilities are real. This is the conflation of epistemology with ontology addressed.
In an entirely causal universe, every event that happens, does so due to what causes such. And the event that causes such does so due to what causes such. The circumstances for each event couldn’t be different, because each cause couldn’t be different.
In the book I’ve written on this topic it is logically explained that X cannot both be the cause of Y and not the cause of Y. Otherwise X and what it is comprised of would be self-contradictory. I go into great lengths in detailing this important understanding out in the book and why such is so incompatible with multiple “real” possibilities (if, in fact, every event has a cause).
But to shorten such up, if X is caused by W, and W cannot be both the cause of X and not the cause of X, then X simply cannot be a different circumstance. It must, for example, based on it’s configuration, be the cause of Y (rather than not the cause of Y, but of Z instead). The same is to be said for W and it’s cause (V). And V and it’s cause (U). To say that any of these could causally happen another way is a logical absurdity (invoking contradiction).
In other words, any such “possibilities” we assess, with the exception of the one that is the only one that can be actualized, can never, ever, be in the ontological realm (without acausality/indeterminism, which holds it’s own problems and is thoroughly addressed in the book). In a causal universe the conditions couldn’t be otherwise than that in which someone decides to fill the box with peanut butter (for example). In a causal universe (or beyond), the box of peanut butter could never have been a box of rocks.
But that’s okay, because peanut butter is delicious!