An Influential Relationship

Influential Arrows

Just Causes and Side Effects
Chapter 14 (“Causality and Observational Predictability”) of Bernard d’Espagnat’s On Physics and Philosophy examines how, and if, we can use the concepts of causation and influence to explain the world.

Reality vs Observations
Taking a break from examining the “notion of reality” d’Espagnat uses this chapter to argue it’s better to predict observations than predict “things as they are.”

Animism vs Empiricism
Aristotle saw causation as related to human will, and even inanimate objects seemed to have some animistic will—as seen when a falling stone somehow desires to return to its natural resting place.

Empiricists went to the other extreme. Physical laws should just be descriptions of events and their regularities. However, what initial conditions are the “cause”? You end up with too many empirical laws.

Mathematical vs Physical Determinism
If two very close points rapidly diverge then they’re not likely to be “physically deterministic.” It’s too hard to calculate their exact paths.

“Strong objectivists” argue that science accumulates knowledge about an underlying reality, not just our experimental observations.

Some strong objectivists argue that “chaotic” behaviour is an example of indeterminism, and others argue initial conditions have to be repeated exactly for us to say deterministic laws apply.

The first approach implies imperfect observations or calculations show reality is indeterministic, but that’s strange since strong objectivists believe in an underlying reality separate from our fuzzy data.

The second approach is a problem since a strong objectivist can’t be absolutely sure the initial conditions won’t be repeated.

Laws vs Predictions
D’Espagnat also criticizes the claim we’ve seen the “end of certainties” just because some calculations make predictions impossible.

He says that’s too harsh as we can still believe in our laws even if sometimes in practice we can make reliable predictions only for the near future.

Classical vs Quantum Indeterminacy
D’Espagnat cautions against regarding chaos theory as some overriding conceptual triumph as it’s grounded on classical concepts of space and time.

Classical physics falters where quantum physics and its apparent indeterminacy excel, particularly on the microscopic level.

Yet d’Espagnat says the defining feature of quantum mechanics is not its indeterminacy but its “weak objectivity.” The theory confines itself to observations of reality, not claims about reality itself.

Individual vs Statistical Determinacy
D’Espagnat agrees with Kant that “regularity in time”—in which one kind of event is followed consistently by another—is a good way to distinguish the empirically real from, say, the events of a dream.

Kant’s “sin of omission” (understandable because of his time and place) was not to consider statistical regularities in which ensemble probabilities are deterministic.

D’Espagnat emphasizes that quantum mechanics makes reliable predictions for observing ensembles of quantum systems, but these are not probabilities of ignorance about individual systems.

At first glance quantum mechanics may seem indeterministic, but if you keep in mind quantum predictions are about observations of multiple systems then it too is deterministic—if only “statistically.”

Laws vs Facts
D’Espagnat warns against “a variant of nihilism” if you don’t pay enough attention to the difference between laws and facts.

He says even Dirac’s musings that universal constants (such as the speed of light) might change over time don’t threaten that distinction.

The nihilistic danger, d’Espagnat says, comes from sociologists, epistemologists, or “pure philosophers” who see in the history of a changing universe a fundamental lack of stability.

They fail to distinguish between laws and facts, or they fail to appreciate the significance of the distinction.

Causes vs Influences
D’Espagnat imagines a Laplace daemon that can possess total knowledge of events in part of the universe.

The fixed speed of light means, in an Einsteinian world, the daemon need only check events in a point’s past light-cone to predict that point’s future.

However, Bell’s Theorem combined with the experiments of Alain Aspect (and others) proved that the locality hypothesis is false.

Add to that the order (in time) of events can vary by reference frame, and we see that (earlier) cause and (later) effect can be ambiguous.

D’Espagnat thus suggests that faster-than-light influences—or “influential relationships”—do exist.

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