Friday, September 28, 2012

Medieval positivist minister

Suppose that a scientific book was published, and the publisher added a forward written by someone else, saying:
To the Reader
Concerning the Hypotheses of this Work

There have already been widespread reports about the novel hypotheses of this work, ...
they will find that the author of this work has done nothing blameworthy. ... Since he cannot in any way attain to the true causes, he will adopt whatever suppositions enable the motions to be computed correctly from the principles of geometry for the future as well as for the past. The present author has performed both these duties excellently. For these hypotheses need not be true nor even probable. On the contrary, if they provide a calculus consistent with the observations, that alone is enough. ...

And if any causes are devised by the imagination, as indeed very many are, they are not put forward to convince anyone that are true, but merely to provide a reliable basis for computation. However, since different hypotheses are sometimes offered ... [one] will take as his first choice that hypothesis which is the easiest to grasp. ...

Therefore alongside the ancient hypotheses, which are no more probable, let us permit these new hypotheses also to become known, especially since they are admirable as well as simple and bring with them a huge treasure of very skillful observations. ...
Would this support or undermine the book? Would it be pro-science or anti-science?

The statement is positivist. It praises the book's theory for its ability to predict observations. This is the core of science.

It is the famous Osiander forward to De revolutionibus orbium coelestium, by Copernicus. Many people have criticized this forward as being anti-science. An encyclopedia said that it "clearly contradicted the body of the work." Arthur Koestler called it a "scandal".

The most anti-science part is this, by the Lutheran minister:
the astronomer will take as his first choice that hypothesis which is the easiest to grasp. The philosopher will perhaps rather seek the semblance of the truth. But neither of them will understand or state anything certain, unless it has been divinely revealed to him.
This suggests that Truth is in the domain of philosophers and Bible-readers, not scientists.

But Osiander is correct. Copermnicus had no reason to be certain of his hypothesis. He had an argument that his model fit the data, and that it was easier to grasp. The model was later replaced by Kepler's and by general relativity, so it was not certain or True.

Arthur Koestler, in The Sleepwalkers, confirms that Osiander meant what he said, citing earlier letters:
Two years earlier, when Copernicus was still hesitating whether to publish the book, he had written to Osiander to pour out his anxieties and to ask for advice. 60 Osiander had replied:

“For my part I have always felt about hypotheses that they are not articles of faith but bases of computation, so that even if they are false, it does not matter, provided that they exactly represent the phenomena… It would therefore be a good thing if you could say something on this subject in your preface, for you would thus placate the Aristotelians and the theologians whose contradictions you fear.” 61

On the same day, Osiander had written on the same lines to Rheticus, who was then in Frauenburg:

“The Aristotelians and theologians will easily be placated if they are told that several hypotheses can be used to explain the same apparent motions; and that the present hypotheses are not proposed because they are in reality true, but because they are the most convenient to calculate the apparent composite motions.”

Prefatory remarks of this kind would induce in the opponents a more gentle and conciliatory mood; their antagonism will disappear “and eventually they will go over to the opinion of the author.” 62
Rheticus has published in support of heliocentrism before Copernicus, and thereby encouraged Copernicus that his book would get a favorable reception.

I think that Osiander's attitude is more scientific than today's academics, who all say that positivism is dead. They make fun of Bible readers, but they have their own ideas about believing in Truths that are independent of observation.

Here is a description of the controversy:
Copernicus was unhappy with this since it had always been his aim to show the true structure of the planetary system rather than some mathematical fiction. Kepler, who saw Copenicus's reply to Osiander said that the astronomer had had no intention of complying with his idea and had decided to maintain his own opinion 'even though the science should be damaged'.

In the event however Osiander did publish a unsigned preface suggesting the heliocentric theory was a hypothesis for computation. Rheticus was furious at this and tried to publish a corrected version without success. Bishop Giese was also outraged, describing the preface as a 'fraud' and writing to Rheticus with the aim of having the preface denounced to the Senate of Nuremberg.

In the event however, Osiander's motives were far from malicious. Osiander was following the custom of the Middle ages which was to propound new theories as hypotheses whose truth remained to be tested in the public forum; this reflected a tradition of instrumentalism that had been applied to astronomy since the time of Ptolemy. He was also making an honest attempt to disarm the defenders of the Aristotelian position and at most he was guilty of an error of judgement. In the event, the label 'hypothesis' applied to the heliocentric theory did open a way for the wide dissemination of its main principles and prepared the ground for the acceptance of the new cosmology.
Stephen Hawking used to call himself a positivist, but his latest book advocates model-dependent realism. It says that "a well-constructed model creates a reality of its own." He ends up arguing for M-theory, which is the dominant paradigm among theoretical physicists but has no connection with observations.

Most people (in ancient and modern times) assume that either Sun goes around the Earth or the Earth goes around the Sun. But it was a gigantic unwarranted assumption to say that one of these is true and one is false. There was no evidence for such a belief. I say that the better scientific attitude is to identify that as an assumption and to admit that it may be false. So Osiander had the better philosophy than Copernicus.

I argue for positivism in my FQXi essay, but admit that is a minority view. But even if I cannot convince you of positivism, I ought to be about to convince you that the sort of positivism shown by Osiander is a completely legitimate scientific view.


  1. Perhaps Copernicus did not fancy being burned at the stake. So a handy way to sidestep the question - what does mathematics really mean?

  2. Copernicus was not worried about being burned at the stake. His book had the endorsement of the Catholic Church, and no one ever got burned for publishing scientific ideas.