There’s really nothing very mysterious about uncertainty. We’re soaking in it every moment of our lives. We generally don’t know what’s happened in the past, we don’t fully know the current state of affairs in the world and we have even less of an idea of how events will unfold. While some have looked to the uncertainty that’s part of the current quantum physical models of the universe, there’s really no need to invoke such esoteric mechanisms. Its part of the nature of being human that we experience the world as uncertain. Yet it appears that in a material world working according to Newtonian physics, there is no real uncertainty. The current state of the universe determines the next state of the universe.
The prospect of a “clockwork universe†is frightening. In the most extreme conception, we live in a universe which began its existence with a set of initial conditions that then is playing out the predetermined events implied in those initial conditions. Whether those initial conditions were intelligently set by a creator or “just happened†doesn’t matter for us,we are each actors playing out our parts in a predetermined script. Theoretically, a sufficiently powerful being could have access to all of the initial conditions and the ability to calculate all of the interactions. Prediction would be easy enough by simply running the calculations needed to predict any future event.
I’m going to unilaterally cut off debate on this interesting topic (author’s privilege!) by assuming that this is exactly the kind of world we live in. I’ll ignore quantum effects because at physical level the world appears to be mostly deterministic. Actually, I believe that the uncertainty at the atomic level makes the clockwork universe conception untenable. It appears that events at some physical level like radioactive decay are truly probabilistic. As long as these random events have effects at a macroscopic level (producing a click in a geiger counter for example) then if the world were started over again with exactly the same initial conditions, it would turn out differently because these random events would be different the second time around.
We can use the famous thought experiment of Schrödinger’s cat to illustrate this.
One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small that perhaps in the course of the hour, one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges, and through a relay releases a hammer that shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.
It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naively accepting as valid a “blurred model” for representing reality. In itself, it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.
Schrödinger has successfully introduced the odd mathematics of quantum uncertainty into the realm of our experience. There are interesting questions about whether the cat is conscious and thus an observer of its own state and whether there is a difference between the unknown and indeterminacy that are beyond the scope of the current discussion. We want to focus on the fact that the quantum event of decay, an event that can’t be predicted only observed to have occurred, can dictate the fate of the cat.
If there was no random decay, the cat walks out of the chamber and continues to influence the world, shedding fur and ending the lives of mice and birds. If the cat is dead when the chamber is opened, there is a different set of events because of the random quantum event of radioactive decay.
But as I think Schrödinger is arguing, to say that reality itself is blurred seems ridiculous. The macroscopic world operates under deterministic Newtonian physics where theoretically every event is mechanistically caused by the immediately preceding state of the system. My next thought is determined by the current state of my brain, not some mystical non-physical spirit that is free of the physics of our deterministic world. There is no quantum level entanglement like our blurred cat where the next thought both exists and does not exist.
We’ve come to the first philosophical barrier in Deciding Better, the nature of free will in a deterministic universe.


