*WARNING: This post contains spoilers for the tv show Devs.*
In Devs a program is created that can analyze all the information in the universe, and so it’s able to simulate everything that has happened in the past and everything that will happen in the future. The argument is that this is possible since all events follow from some causal event and determined precisely by the laws of physics.
But something strange happens when people are able to see their own future. Once they’ve seen what they will do in the future they are compelled to carry out that future. As the show presents it, they have no choice. But does this make sense?
I believe the problem isn’t with the concept of determinism, but rather the concept of a machine that can predict the future. We might imagine that the universe consists of a very large but still finite amount of information, which makes the existence of the machine seem plausible. But in order to accurately predict my future and show it to me would require being able to process an infinite amount of information in a finite amount of time.
Imagine that I decide to raise either my right hand or my left hand. Then I decide that whatever I see on the prediction machine I will do the opposite. If I see myself raising my left hand I will raise my right hand, and vice versa. Now in order for the computer to know what I will do next, it must consider what will happen when it shows me my future as part of its calculation.
Let’s say that it has calculated that I will raise my right hand. But knowing that once I see the prediction I will raise my left hand, it instead concludes I will raise my left hand. But of course it must then factor into its calculation what happens when I see this prediction and decide to raise my right hand. This process will go on forever. Thus the calculation of which hand I raise after seeing the prediction falls into an infinite loop.
If we accept that it’s not possible to complete an infinite loop in a finite amount of time, then logically the program cannot exist in the first place.