As found in N.R. Hanson, Patterns of Discovery. (Cambridge University Press, London, 1961.)
[Induction] sets out with a theory and it measures the degree of concordance of that theory with fact. It never can originate any idea whatever. No more can Deduction. All the ideas of science come to it by way of Abduction. Abduction consists in studying facts and devising a theory to explain them. Its only justification is that if we are ever to understand things at all, it must be that way. Abductive and inductive reasoning are utterly irreducible, either to the other or to Deduction, or Deduction to either of them… C.S. Pierce, Collected Papers, V. 5, # 146.
What is it to supply a theory? It is to offer an intelligible, systematic, conceptual pattern for the observed data. The value of this pattern lies in its capacity to unite phenomena which, without the theory, are either surprising, anomalous, or wholly unnoticed. Democritus’ atomic theory avoids investing atoms with those secondary properties requiring explanation. It provides a pattern of concepts whereby the properties the atom does possess – position, shape, motion – can as a matter of course, account for the other “secondary” properties of objects. The price paid for this intellectual gain is unpicturability. N.R. Hanson, Patterns of Discovery, p. 121.
Physical theories provide patterns within which data appear intelligible. They constitute a “conceptual Gestalt”. A theory is not pieced together from observed phenomena; it is rather what makes it possible to observe phenomena as being of a certain sort, and as related to other phenomena .Theories put phenomena into systems. They are built up ‘in reverse’ – retroductively. A theory is a cluster of conclusions in search of a premiss. From the observed properties of phenomena the physicist reasons his way toward a a keystone idea from which the properties are explicable as a matter of course. The physicist seeks not a set of possible objects, but a set of possible explanations. Hanson, p. 90.
Kepler’s first Martian theory, the “Vicarious Theory“, rested on one principle, fundamental to the astronomical tradition into which he was born. The planet moved in a perfect circle. This alone as proper for celestial bodies. They alone exhibited what Aristotle called “perfect motion.”
However, in these terms the calculated distances required Mars eccentricity to be very great, so great, in fact, that the resulting equations concerning the orbit’s elements were either false or inconsistent. Then Kepler determined these elements b other methods. The result was the the method of equal areas in equal times – on which Kepler was come to rely – gave errors of 8′ in excess and defect. (Were the orbit really circular, this method could not have given errors greater than 1′.)
Kepler was half-inclined to ascribe the errors to imperfections in the method of areas. But he slowly came to suspect that perhaps his predecessors of the previous 2000 years were hasty in thinking the planetary orbits circular. Hindsight makes us underestimate the strength of this ancient maxim; Kepler’s challenge seems natural to us. But no bolder exercise of imagination was every required: Kepler dared to ‘pull the pattern’ away from all the astronomical thinking there had ever been. Not even the conceptual upsets of our century of natural science (20th century) required such a break with the past. Before Kepler, circular motion was to the concept of planet as ‘tangibility’ is to our concept of ‘physical object’. If intangible physical objects are inconceivable to us, so were non-circular planetary orbits to Kepler’s predecessors, and contemporaries. Remember, Tycho and Galileo never made this break. Hanson, p 74
For Kepler and Tycho, the elements of their experiences are identical; but their conceptual organization is vastly different. Can their visual fields have a different organization? Then they can see different things in the east at dawn.
It is this sense in which :Tycho and Kepler do not observe the same thing which must be grasped if one is to understand disagreements within microphysics. Fundamental physics is primarily a search for intelligibility – it is philosophy of matter. Only secondarily is it a search for objects and facts (though the two endeavors are as hand and glove). Microphysicists seek new modes of conceptual organization. It that can be done the finding of new entities will follow. Gold is rarely discovered by one who has not got the lay of the land. Hanson, p. 18.
The time factor could receive due weight in this geometrical representation – the successes of Beeckman and the later Galileo prove this. But it is understandable why this factor should so long have been overlooked: thinking new thoughts in a conceptual framework not designed to express them requires unprecedented physical insights. In the history of physics, few could sense the importance of things not yet expressible in current idioms. The task of the few has been to find means of saying what is for others unsayable. There was no derivative with which Galileo could attack the problem of constant acceleration, yet ultimately he fought through to what is essentially just this unifying idea. Newton had to build the whole theory of fluxions to speak the truth fully. Physics today is a mountain of mathematical formalisms; some of these express, explain and unify our observations. Hanson, p .46