There is a remarkably persistent picture of scientific knowledge.
First there is the world.
Then there is the observer.
The observer looks at the world, measures it, describes it and constructs theories about it.
The ideal observer is detached. The world is simply there, independently of being observed.
This seems so obvious that we rarely notice it as a philosophical assumption.
Yet it has a history.
And quantum mechanics makes that history difficult to ignore.
The spectator
The image of the observer as spectator is closely related to the classical picture of things we encountered in the first two posts.
There are objects.
They possess properties.
They interact according to laws.
The observer stands outside this arrangement and discovers what is happening.
Even if observation is difficult, the principle seems clear: what is observed exists independently of the act of observation.
A perfectly detached observer would therefore be the ideal.
This picture has obvious practical value.
Scientists try to minimise interference, control experimental conditions and distinguish the system being studied from the apparatus used to study it.
But a practical ideal of controlled observation is not the same thing as an ontology of detached observation.
Quantum mechanics makes that distinction increasingly important.
Measurement is an interaction
A quantum measurement is not simply a window through which information flows from an already determinate object into an already detached mind.
A physical system interacts with another physical system.
The measuring apparatus becomes correlated with the system.
An outcome is produced.
Something physical happens.
This seems almost embarrassingly obvious when stated that way.
But it changes the philosophical picture.
The measurement is not outside the physical process.
It is part of the physical process.
The apparatus is not nowhere.
The observer is not nowhere.
The interaction occurs somewhere, at some time, under particular physical conditions.
The distinction between observer and observed may therefore be useful without being fundamental.
The measurement problem
This is where the familiar measurement problem acquires philosophical significance.
Quantum theory describes physical systems using states that can evolve into superpositions of possible outcomes.
Yet measurements produce determinate outcomes.
Why?
Different interpretations answer differently.
Perhaps the wave function collapses.
Perhaps all outcomes occur in different branches.
Perhaps hidden variables determine the result.
Perhaps the quantum state is not a description of physical reality in the ordinary sense.
Perhaps something else is required.
These are important possibilities.
But beneath them lies a prior question:
What exactly is a measurement?
If measurement is imagined as something an observer does to an otherwise complete quantum system, the classical picture is quietly preserved.
The observer remains outside.
Reality remains inside.
The measurement is the bridge between them.
But if measurement is itself a physical relation, that bridge may be unnecessary.
There is no outside observer looking into reality.
There is only one physical process in which different systems interact.
The Copenhagen temptation
The historical Copenhagen interpretation is often associated with the claim that quantum mechanics concerns what can be said about experimental outcomes rather than an underlying classical reality.
Whatever one thinks of the many versions of Copenhagen, its enduring importance is that it refused to pretend that the classical picture could simply be carried over unchanged.
But this creates another temptation.
If the observer is unavoidable, perhaps consciousness is what completes the measurement.
This is where things can become unnecessarily mysterious.
There is no need to move from “measurement is a physical interaction” to “human consciousness creates physical reality.”
A measuring apparatus does not have to be conscious to interact with a quantum system.
A photographic plate can record an event.
A detector can register a particle.
A physical system can become correlated with another physical system without anyone looking at the result.
The important philosophical point is therefore not that the mind creates the world.
It is that the observer cannot be conceptually extracted from the physical world in order to provide a view of that world from outside it.
The Cartesian inheritance
This is where the Cartesian inheritance becomes visible.
Descartes gave philosophy an especially powerful distinction between thinking subject and extended world.
Whatever the details of Cartesian philosophy, the distinction became part of the modern imagination.
Here is the world.
Here is the mind that knows the world.
Scientific objectivity can then appear to require the mind to minimise its involvement with what it observes.
But there is a problem.
The scientist is also a physical organism.
The laboratory is also part of the physical world.
The apparatus is part of the physical world.
The interaction between apparatus and system is part of the physical world.
And the subsequent observation of the measurement is another physical process within it.
There is no privileged location outside the chain.
We do not first leave the world in order to know it.
We know the world from within the world.
This does not destroy objectivity
It is important not to turn this into the opposite error.
If the observer cannot stand outside the world, it does not follow that reality is subjective.
The moon does not disappear when nobody looks at it.
The apparatus does not produce arbitrary results because a human being happens to be present.
Physical systems interact whether or not anyone is watching.
Indeed, the extraordinary success of physics depends upon the fact that the world is capable of resisting our expectations.
We make a prediction.
We perform an experiment.
The result may surprise us.
That surprise is precisely what makes inquiry possible.
Objectivity therefore need not mean detachment from relation.
It can mean reliable participation in relations that constrain what we can say.
The scientist is not objective because they have escaped the world.
They are objective because the world can answer back.
The observer as participant
This gives us a different conception of scientific observation.
The observer does not manufacture the phenomenon.
But neither are they merely looking through a transparent window at something completely independent of the conditions under which it becomes observable.
They participate in an experimental arrangement.
They choose what to measure.
They construct instruments.
They establish conditions.
They formulate questions.
They interpret results.
The physical system responds.
The apparatus responds.
The result constrains the interpretation.
The interpretation informs the next experiment.
Inquiry becomes a feedback process.
This does not weaken science.
It is very close to what science actually does.
What changes is the philosophical description of what it means to do it.
The impossible view from nowhere
We can now see why the idea of an absolutely detached observer is problematic.
To observe the whole universe from outside would require an observer who was not part of the universe.
But then the observer would not be observing the whole universe.
And if the observer is part of the universe, their observation is one event among the events being observed.
The problem is not that we have failed to build a sufficiently powerful telescope.
It is conceptual.
There is no physical standpoint from which reality as a whole can be observed without participation in reality.
This does not make knowledge impossible.
It makes knowledge relational.
We learn about the world through interactions within the world.
From observer to relation
The philosophical shift is therefore subtle but profound.
The classical picture says:
world → observer → observation
The relational picture says:
world → interaction → observation
The observer is not removed.
They are relocated.
They become one participant in a larger physical and conceptual process.
The distinction between observer and observed remains useful because different systems occupy different roles in an experiment.
But the roles are relational rather than absolute.
A detector is an observer in one sense.
A scientist is an observer in another.
The system being measured can become part of the measuring process.
The boundaries matter.
But the boundaries are not walls between two fundamentally different kinds of reality.
What quantum mechanics may be telling us
This is perhaps why quantum mechanics has generated so many competing interpretations.
The mathematics is extraordinarily successful.
The conceptual picture is not.
And when a theory works while its ordinary interpretation becomes unstable, we face a choice.
We can keep modifying the physics until the old philosophical picture is restored.
Or we can ask whether the picture itself has become the problem.
The second possibility is more unsettling.
Perhaps quantum mechanics is not telling us that observers possess mysterious powers.
Perhaps it is telling us something simpler:
there was never a detached observer standing outside physical reality.
There were always only physical systems entering into relations.
Some of those systems became measuring instruments.
Some became organisms.
Some became scientists capable of constructing theories about what was happening.
And eventually one part of the world became capable of asking how the world could be known by a part of itself.
That is a very different philosophical picture.
The observer does not stand outside reality.
The observer is one of the things reality has become capable of doing.
And if that is so, another classical assumption becomes difficult to maintain.
Perhaps the future is not simply something that already exists in determinate form, waiting for an observer to discover it.
Perhaps what becomes actual can change what remains possible.
That is the problem we need to turn to next.
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