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deity surely, one of those whose task is to encourage the elect of this world. His post at the Stiftsschule carried with it the title of calendar maker for the province of Styria. The previous autumn, for a fee of twenty florins from the public coffers, he had drawn up an astrological calendar for the coming year, predicting great cold and an invasion by the Turks. In January there was such a frost that shepherds in the Alpine farms froze to death on the hillsides, while on the first day of the new year the Turk launched a campaign which, it was said, left the whole country from Neustadt to Vienna devastated. Johannes was charmed with this prompt vindication of his powers (and secretly astonished). A sign, yes, surely. He set to work in earnest on the cosmic mystery.
    He had not the solution, yet; he was still posing the questions. The first of these was: Why are therejust six planets in the solar system? Why not five, or seven, or a thousand for that matter? No one, so far as he knew, had ever thought to ask it before. It became for him the fundamental mystery. Even the formulation of such a question struck him as a singular achievement.
    He was a Copernican. At Tübingen his teacher Michael Mästlin had introduced him to that Polish master's world system. There was for Kepler something almost holy, something redemptive almost, in that vision of an ordered clockwork of sun-centred spheres. And yet he saw, from the beginning, that there was a defect, a basic flaw in it which had forced Copernicus into all manner of small tricks and evasions. For while the
idea
of the system, as outlined in the first part of
De revolutionibus,
was self-evidently an eternal truth, there was in the working out of the theory an ever increasing accumulation of paraphernalia-the epicycles, the equant point, all that-necessitated surely by some awful original accident. It was as if the master had let fall from trembling hands his marvellous model of the world's working, and on the ground it had picked up in its spokes and the fine-spun wire of its frame bits of dirt and dead leaves and the dried husks of worn-out concepts.
    Copernicus was dead fifty years, but now for Johannes he rose again, a mournful angel that must be wrestled with before he could press on to found his own system. He might sneer at the epicycles and the equant point, but they were not to be discarded easily. The Canon from Ermland had been, he suspected, a greater mathematician than ever Styria's calendar maker would be. Johannes raged against his own inadequacies. He might know there was a defect, and a grave one, in the Copernican system, but it was a different matter to find it. Nights he would start awake thinking he had heard the old man his adversary laughing at him, goading him.
    And then he made a discovery. He realised that it was not so much in what he
had
done that Copernicus had erred: his sin had been one of omission. The great man, Johannes now understood, had been concerned only to see the nature of things demonstrated, not explained. Dissatisfied with the Ptolemaic conception of the world, Copernicus had devised a better, a more elegant system, which yet, for all its seeming radicalism, was intended only, in the schoolman's phrase, to save the phenomena, to set up a model which need not be empirically true, but only plausible according to the observations.
    Then had Copernicus believed that his system was a picture of reality, or had he been satisfied that it agreed, more or less, with appearances? Or did the question arise? There was no sustained music in that old man's world, only chance airs and fragments, broken harmonies, scribbled cadences. It would be Kepler's task to draw it together, to make it sing. For truth was the missing music. He lifted his eyes to the bleak light of winter in the window and hugged himself. Was it not wonderful, the logic of things? Troubled by an inelegance in the Ptolemaic system, Copernicus had erected his great monument to the