You think I consider myself a lofty personage. I do not. High honours amp; offices I have never had. I live here on the stage of the world as a simple, private man. If I can squeeze out a portion of my salary at court, I am happy not to have to live entirely on my own means. As for the rest, I take the attitude that I serve not the Emperor, but rather the whole human race amp; posterity. In this confident hope, I scorn with secret pride all honours amp; offices, and also those things which they bestow. I count as the only honour the fact that by divine decree I have been put near the Tychonic observations.
Forgive, then, please, any slights that have been offered you in ignorance by
your friend, K
Wenzel House Prague Christmastide 1606
Hans Georg Herwart von Hohenburg: at München
Salve. This will, I fear, be but the briefest of scribbles, to wish you amp; your family all happiness of the season. The court is busy with preparations for the festivities, and consequently I am forgotten for the moment, and hence am allowed a little time to pursue my private studies undisturbed. Is it not strange, how, at the most unexpected of moments, the speculative faculty, having just alighted from a long amp; wearisome flight, will suddenly take wing again immediately, and soar to even loftier heights? Having lately completed my Astronomia nova, and looking forward to a year or two of much needed rest amp; recuperation, here I am now launching out again, with renewed fervour, upon those studies of world harmony, which I interrupted seven years ago in order to clear away the little task of founding a new astronomy!
Since, as I believe, the mind from the first contains within it the basic amp; essential forms of reality, it is not surprising that, before I have any clear knowledge of what the contents will be, I have already conceived the form of my projected book. It is ever thus with me: in the beginning is the shape! Hence I foresee a work divided into five parts, to correspond to the five planetary intervals, while the number of chapters in each part will be based upon the signifying quantities of each of the five regular or Platonic solids which, according to my Mysterium, may be fitted into these intervals. Also, as a form of decoration, and to pay my due respects, I intend that the initials of the chapters shall spell out acrostically the names of certain famous men. Of course, it is possible that, in the heat of composition, all of this grand design might be abandoned. But it will be no matter.
I have taken as my motto that phrase from Copernicus, in which he speaks of the marvellous symmetry of the world, and the harmony in the relationships of the motion amp; size of the planetary orbits. I ask, in what does this symmetry consist? How is it that man can perceive these relationships? The latter question is, I think, quickly solved-I have given the answer just a moment ago. The soul contains in its own inner nature the pure harmonies as prototypes or paradigms of the harmonies perceptible to the senses. And since these pure harmonies are a matter of proportion, there must be present figures which can be compared with each other: these I take to be the circle and those parts of circles which result when arcs are cut off from them. The circle, then, is something which occurs only in the mind: the circle which we draw with a compass is only an inexact representation of an idea which the mind carried as really existing in itself. In this I take issue strenuously with Aristotle, who holds that the mind is a tabula rasa upon which sense perceptions write. This is wrong, wrong. The mind learns all mathematical ideas amp; figures out of itself; by empirical signs it only remembers what it knows already. Mathematical ideas are the essence of the soul. Of itself, the mind conceives equidistance from a point, and out of that makes a picture for itself of a circle, without any sense perceptions whatever. Let me put it thusly: If the mind had never shared an eye, then it would, for the conceiving of the things situated outside itself, demand an eye and prescribe its own laws for forming it. For the recognition of quantities which is innate in the mind determines how the eye must be, and therefore the eye is so, because the mind is so, and not vice versa. Geometry was not received through the eyes: it was already there inside.
These, then, are some of my present concerns. I shall have much to say of them in the future. For now, my lady wife desires that the great astronomer issue forth into the town to purchase a fat goose.
Fröhliche Weihnachten! Johannes Kepler
Loretoplatz Hradcany Hill Prague Easter Day 1605
David Fabricius: in Friesland
As I have delayed long in my promise of a further letter, so it is right all the same that I should sit down now, on this festival of redemption, to tell you of my triumph. As, my dear Fabricius, what a foolish bird I had been! All along the solution to the mystery of the Mars orbit was in my hands, had I but looked at things correctly. Four long years had elapsed, from the time I acknowledged defeat because of that error of 8 minutes of arc, to my coming back on the problem again. In the meantime, to be sure, I had gained much skill in geometry, and had invented many new mathematical methods which were to prove invaluable in the renewed Martian campaign. The final assault took two, nearly three more years. Had my circumstances been better, perhaps I would have done it more quickly, but I was ill with an infection of the gall, and busy with the Nova of 1604, and the birth of a son. Still, the real cause of the delay was my own foolishness amp; shortness of sight. It pains me to admit, that even when I had solved the problem, I did not recognise the solution for what it was. Thus we do progress, my dear Doctor, blunderingly, in a dream, like wise but undeveloped children!
I began again by trying once more to attribute a circular orbit to Mars. I failed. The conclusion was, simply, that the planet's path curves inwards on both sides, and outwards again at opposite ends. This oval figure, I readily admit, terrified me. It went against that dogma of circular motion, to which astronomers have held since the first beginnings of our science. Yet the evidence which I had marshalled was not to be denied. And what held for Mars, would, I knew, hold also for the rest of the planets, including our own. The prospect was appalling. Who was I, that I should contemplate recasting the world? And the labour! True, I had cleared the stables of epicycles amp; retrograde motions and all the rest of it, and now was left with only a single cartful of dung, i.e. this oval-but what a stink it gave off! And now I must put myself between the shafts, and draw out by myself that noisome load!
After some preliminary work, I arrived at the notion that the oval was an egg shape. Certainly, this conclusion involved some geometrical sleight of hand, but I could not think of any other means of imposing an oval orbit on the planets. It all seemed to me wonderfully plausible. To find the area of this doubtful egg, I computed 180 sun-Mars distances, and added them together. This operation I repeated 40 times. And still I failed. Next, I decided that the true orbit must be somewhere between the egg shape amp; the circular, just as if it were a perfect ellipse. By this time, of course, I was growing frantic, and grasping at any straw.