Sometimes a new possibility appears because the evidence has accumulated until a particular structure becomes compelling.
Sometimes something stranger happens.
The evidence remains much the same, but someone changes the place from which it is understood.
The Copernican revolution is a particularly revealing example.
It is often told as the discovery that the Earth moves around the Sun rather than the Sun around the Earth. But that formulation makes the achievement sound like the discovery of a new astronomical fact.
Copernicus did something more subtle.
He moved the centre.
The world before Copernicus
By the sixteenth century, the Ptolemaic astronomical system was already extraordinarily sophisticated.
It was capable of representing the apparent movements of the planets with considerable mathematical precision. Its complexity had grown, but complexity is not the same thing as failure.
The problem was therefore not simply that observations had become impossible to explain.
There was another problem.
The existing astronomical system had made the Earth the fixed centre of a universe whose celestial motions were organised around it. Copernicus wondered whether this arrangement was necessary.
What if it wasn't?
What if the apparent motion of the heavens was partly a consequence of the Earth's own motion?
This is a very different kind of question from asking which curve best fits a set of observations.
It asks:
What if the frame within which the observations are organised is not privileged?
A change of centre
The striking thing about heliocentrism is that it does not initially add a new observation.
The planets still appear in the sky as they did before.
The observations available to Copernicus do not suddenly change when the Earth is moved from the centre.
What changes is the relational organisation of those observations.
The retrograde motion of Mars, for example, can be understood differently if the Earth is itself moving around the Sun. What had appeared to be a peculiar motion of another planet can become an effect of the changing relation between two moving bodies.
The phenomenon has not changed.
The relation through which it is understood has changed.
This is a recurring feature of conceptual transformation.
A thing that appears anomalous within one conceptual arrangement can become ordinary within another.
The anomaly was never necessarily a property of the thing itself.
It may have belonged to the relation between the phenomenon and the framework used to construe it.
But was heliocentrism forced by the evidence?
Not in any simple sense.
This is what makes Copernicus especially interesting.
The astronomical observations available in his time did not uniquely establish heliocentrism. Indeed, the Ptolemaic system could represent the apparent motions of the planets.
Nor did Copernicus immediately provide the decisive physical explanation that would later make the new system compelling.
His system still retained many inherited assumptions about circular motion and uniformity.
So the Copernican revolution cannot simply be described as the inevitable consequence of better observations.
The conceptual possibility came first.
Copernicus made it possible to ask:
What would astronomy look like if the Earth were not the centre?
That question reorganised the space of possible explanations.
Possibility before proof
This gives us an important addition to our emerging account.
With Darwin, the intellectual environment increasingly afforded a particular explanatory possibility.
With DNA, a network of empirical constraints helped select a structure.
With Copernicus, a new possibility emerged because an apparently fixed relation was made variable.
The Earth did not have to be the centre.
Once that became thinkable, a whole collection of astronomical relations could be reorganised.
This is an important characteristic of conceptual possibility.
Sometimes what prevents us from seeing a possibility is not a lack of information.
It is the assumption that some relation is necessary when it is only customary.
The centre may be moved.
The boundary may be moved.
The distinction between two categories may be questioned.
The hierarchy may be inverted.
A conceptual revolution can begin with a very small question:
Does this really have to be here?
The cost of moving the centre
But moving the centre is not free.
A conceptual framework is not merely a collection of propositions. It is a network of mutually supporting relations.
Change one relation and others begin to move.
If the Earth moves, what happens to falling objects?
Why don't we feel the motion?
What holds the planets in their paths?
Why does the sky appear to move?
What becomes of the traditional distinction between terrestrial and celestial motion?
Copernicus could change the astronomical centre without immediately answering all these questions.
That is part of the nature of conceptual innovation.
A new possibility does not have to arrive with a complete theory.
Sometimes its first achievement is simply to make a different set of questions possible.
Kepler will inherit the possibility
This is why the Copernican revolution cannot be understood in isolation.
Once the Earth has been displaced from the centre, the astronomical problem changes.
Johannes Kepler inherits Tycho Brahe's exceptionally precise observations and asks how planetary motion can be represented within the new framework.
The answer will not be what he expects.
The planets do not move in perfect circles.
They move in ellipses.
Here the mode of conceptual evolution changes again.
Copernicus opened a possibility by moving the centre.
Kepler will discover a structure through constraint.
The new conceptual space makes a new question possible; the evidence then begins to reshape the possibilities within it.
This is why conceptual evolution is rarely a sequence of isolated flashes of genius.
A possibility opened by one thinker can become the affordance for another thinker's discovery.
The second discovery may in turn make the first intelligible in ways its originator could not have anticipated.
A centre is more than a location
There is also something deeper in the idea of the centre.
A centre is not merely a point in space.
It is a way of organising relations.
To call something the centre is to specify how other things are related to it.
The Earth-centred cosmos therefore did more than place the Earth in a particular location. It organised the conceptual relations among Earth, heaven, motion and observation.
Moving the centre changed those relations.
This helps explain why conceptual change can be so disruptive even when the empirical objects remain the same.
The stars do not move differently because Copernicus changes his model.
The planets do not suddenly acquire new trajectories.
What changes is the relational structure through which their movements become intelligible.
And once that structure changes, the world appears differently.
The possibility of another world
There is therefore something almost paradoxical about conceptual discovery.
A new concept can reveal possibilities that were always physically available but were not previously available as possibilities for thought.
The Earth had always been capable of moving around the Sun.
But heliocentrism required more than that physical possibility.
It required the conceptual possibility of treating the Earth's motion as fundamental to the explanation of what appeared to be celestial motion.
This distinction matters.
There can be possibilities in the world that are not yet possibilities within a conceptual system.
Conceptual evolution partly consists in bringing these two spaces into new relations.
The world does not wait for us to conceptualise it.
But what the world can become for thought depends upon the concepts through which its relations are organised.
When the centre moves
Copernicus therefore gives us a third way in which concepts can become possible.
Darwin showed us convergence: an idea can become increasingly afforded by an intellectual environment until independent thinkers arrive at it.
Watson and Crick showed us constraint: a structure can emerge as multiple pieces of evidence become mutually constraining.
Copernicus shows us recentring: a possibility can emerge when a relation that seemed fixed is treated as variable.
The centre moves.
And once it does, the possibilities move with it.
This does not mean that every conceptual revolution begins by changing the centre. Nor does it mean that Copernicus simply invented heliocentrism out of nothing.
His work depended upon an immense inheritance of astronomical observation, mathematical technique and earlier cosmological thought.
But the crucial act was not the discovery of another observation.
It was the discovery that the organisation of the observations could be otherwise.
That is a profound kind of possibility.
Before Copernicus, the question was largely:
How can the heavens be represented from the centre?
After Copernicus, another question became available:
What happens if the centre itself moves?
Sometimes, to make a new world of thought possible, we do not need more facts.
We need to discover that where we are standing is not where we have to stand.
No comments:
Post a Comment