“We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes.”
—Pierre Simon Laplace, A Philosophical Essay on Probabilities
Laplace’s idea has intrigued and disturbed over the years. The general thinking is that quantum mechanics rendered Laplace’s position moot, as you cannot know both the exact position and the exact motion of a particle. I believe, however, that Laplace’s position fails even without quantum mechanics. Here’s why.
Laplace’s posits an all knowing intellect, but then places that intellect outside of, and utterly passive to, the Universe. There are two problems with this. First, by definition, nothing can be outside the Universe. Second, it is completely arbitrary to make this all-knowing intellect passive to the material world. Why should we not assume that this intellect is itself like a typical scientist, who would use its knowledge to try to make the world better? If we assume such an intellect, then Laplace’s conclusion quickly falls apart.
If the intellect modifies the world based on its knowledge, then it has to have a pre-knowledge of how it will change the world and include that in its analysis of the world. But with this knowledge it can change its own behavior, and so it would have to include that in its analysis and so on ad infinitum. Once we assume the all-knowing agent is in the universe and active, then we have to come to the conclusion that the future would be uncertain for this all knowing, active being.**
While all this is quite theoretical, it actually points to the reality of our world. Scientific knowledge has certainly not made our world more certain and predictable, quite the opposite. Yes, we can predict lunar and solar eclipses and the orbits of the planets and satellites to great specificity, but down here on earth the situation is much different.
People living in the world prior to the rise of science had a fairly good sense of what the world of their children’s children’s children would be like – it would be fairly similar to the world they inhabited. Most of the time this would be correct. My parents, who were born early in the 20th Century could scarcely have imagined in their youth the world that I now live in with its nuclear weapons, space travel, computers, the Internet, exponential population increase, etc. Similarly, I have little sense of the world my children will inhabit if they live to be my age. We imagine that the future will be filled with new technologies, but our past experience tells us that the technologies we imagine are not likely to be those that actually appear.
We do not know how creative minds create, but feedback is obviously important. The feedback that spurs creativity is a relationship between a dynamic mind and a dynamic world -- mind changes world, world changes mind in an ever iterative spiral. Dynamic, interactive relationships cannot be reduced, as to reduce to one side of the relationship or the other is to get an incomplete picture. If this aspect of the world cannot be reduced, Laplace’s assumption about the universal validity of reductionism is insufficient. In the end, Laplace’s universe is an imaginary one. Its invention, however, had significant causal effects on our little earth. The view it presented helped initiate the Romantic Movement in the arts. Now that is something that I suspect Laplace didn’t predict.
** (By this same reasoning, a loving god that occasionally changed the course of the world’s events because of that love could not be omniscient – the occasions and results of its love ultimately would be mysterious even to it. Indeed, the concept of love without the accompanying concept of mystery signifies nothing.)