The only way to make Determinism scary is to circumvent the definition of the universe by positing some entity (god or a LaPlacean daemon) outside of the deterministic system, peering in on it. The term universe, of course, refers to all of existence and could simply be adjusted to include that strange, powerful entity, in order to save us from the scary implications of Determinism. We are saved because a LaPlacean daemon could not possibly predict the future, even “in theory,” if it is placed inside a deterministic system instead of mysteriously outside of it. When a determinist asserts the proposition that “in theory” a LaPlacean daemon could tell you in advance what you would do, given the position and velocity of every existent molecule, he is simply wrong. It could not, even in principle, make such a calculation. I don’t mean this in any kind of practical sense, like we couldn’t practically fashion a computer that could make such calculations, or that the universe extends infinitely in all directions thus making such a calculation impossible due to the infinite amount of information it would have to process. I mean, simply, that this calculation, if it were to be done, would pollute its own results. If anyone were to look upon the results of such a calculation, even for a second, it would change their future actions, thus changing the future that was predicted by the calculation. The machine, if infinitely precise, would have caught this fact, and factored it into the calculation, thus forever obliterating the world-that-would-have-been! So the answer that the machine would produce would not, in fact, be the answer to the proposed question. Thus, you could never know what the future would have been had you not consulted the omniscient artillect. But even a prediction of the changed future would be impossible, for the machine would have to know the outcome of its calculation beforehand in order to know how its handlers would receive the news and alter their choices. The machine cannot know the outcome of its calculation before or during the calculation! Even if the machine didn’t tell anyone of the results of its calculation, this calculation would nonetheless have changed the future course of deterministic system because any calculation would require the machine to enter its own current conditions, which would change every time it has produced even a private result from a calculation, thus changing the system (albeit slightly). Thus, it is impossible, even in principle, to make a machine, even one that somehow has infinite computing capacity, that can perfectly predict future outcomes of a deterministic world of which it is a part. We could only make such a machine that would change future outcomes of the deterministic world and tell us of the changes. This is precisely what the human mind does though! It makes predictions which alter the outcome of the deterministic system! The future state of the universe is not “inevitable,” or “unavoidable,” for precisely this reason: that beings exist in it that can predict future states of the system and think up alternatives. This is just Dan Dennett’s argument that humans are the best “avoiders” that evolution has yet produced, and that the existence of any avoiders renders the fatalistic claim that the future is inevitable (meaning “unavoidable”) patently false and senseless.
To illustrate, lets look at Oedepus Rex and assume Determinism. This cleverly penned story skirts the power of human deliberation in order to work. For example, having recieved the prediction about their son’s future, the parents could have made sure that their son was truly dead and it would have been physically impossible for the prophecy to come true. If Oedepus consulted the Oracle and learned of his horrible fate he could simply choose never to kill or marry anyone, thus ensuring that his prophecied fate could not possibly come to pass. The Oracle would have to have known that Oedepus was the kind of guy who was not bright enough to think of these alternatives for her prediction to be valid. Luckily for us, we are bright enough to think of alternatives, making it impossible for even an omniscient oracle to give us predictions about our future that we could not avoid and thus prove wrong. The only way she could do it would be to be exceptionally cruel and vague, as the Oracle at Delphi did in the famous story of the king who consulted her about a war he was planning and met with the following prophecy: “a great kingdom will fall.” The Oracle had to have known that this was a rather dumb king, one who was incapable due to hubris or pure stupidity of interpreting (even for a second) her pronouncement from a less self-glorifying perspective. Once again, we are lucky enough to be smarter than such kings! The point, however, is that the oracle argument requires the oracle to purposefully trap or trick someone for her predictions to work. If the oracle in this last story had told the king the truth more literally (that his great kingdom would fall), it would obviously not have fallen (as the king would abandon his plans for war), thus making the prediction false and/or impossible to make in the first place. Thankfully, we don’t have to worry about omniscient, malicious oracles and should find comfort in the fact that though we are built into this deterministic system, we are nonetheless determined to be limited oracles ourselves. Moreover, we can live by maxims which make certain potential futures truly impossible. If we were in Oedepus’ shoes and recieved his exact reading, we could erect a maxim prohibiting all marriage and all killing, thus making the outcome of the prediction an impossible one. Most importantly though, the fact that we are determined to abhor the thought of killing our own father makes it possible to motivate a strict observance of our own maxim–it grants us Sartre’s power of “No!” or the power to categorically close off certain potential futures from coming to pass. In the case of oracles, this power of “No!” makes any precise prediction of our future truly impossible.
Imagine a benevolent Delphic Oracle, one who could not possibly tell a lie or perform a trick, who looked into the king’s future, saw the destruction of his empire, and told him: “your empire will fall if you go to war, but because you have consulted me and heard this, you will of course not go to war and no kingdom will fall.” The strange thing about humans is that we can also be irrational, stubborn, and indignant. Justifiably pissed off for being called a worthless warlord who can’t win a war and runs from one if he thinks he can’t, the warlord could then choose to go to war as he has the requisite motives to impel such an action. Once again human stubbornness and will-to-freedom make any such prediction a practical and theoretical impossibility. The oracle could go one iteration deeper, telling the king that his indignant act of war would also be ill-fated. In fact, she could keep going indefinitely, telling him every possible outcome of every possible choice, and then conclude that he would do such and such. Once again pissed off and indignant at the suggestion that this is all he could do and all that he would do, the king decides to take his sword out and run her through. There are three interesting points here: 1) the oracle would have to perform an infinite amount of iterations, because there are an infinite amount of physically possible actions we can pursue, 2) we are determined to abhor the idea of fatalism and could thus be motivated to defy any definitive, oracular prediction, and 3) our everyday experience of introspection is exactly like consulting this benevolent oracle. We don’t get to choose what we hear from her, for she speaks only the truth, but we can choose to keep asking questions and demanding iteration after iteration until we arrive at an outcome we like. That is human freedom. Even if we had a genetically determined “baseline” propensity to introspect only so much, it doesn’t matter, because our minds are versatile enough to enlist the other motivational drives to impel us to think and introspect more than this baseline, at least to the extent to which we want to satisfy our other drives.