Carl Hufman is one of the most important contemporary scholars of Pythagoreanism. While no writings of Pythagoras survive (and probably none ever existed in the first place), Huffman has produced editions of the extant fragments from the writings of the early Pythagorean philosophers Philolaus and Archytas, which are of inestimable value to anyone with any interest in Pythagoreanism.
Here is how Huffman describes the cosmology of Pythagoras (from his Stanford Encyclopedia of Philosophy entry -- Huffman also wrote the entries for Philolaus and Archytas):
It remains controversial whether [Pythagoras] engaged in the rational cosmology that is typical of the Presocratic philosopher/scientists and whether he was in any sense a mathematician. The early evidence suggests, however, that Pythagoras presented a cosmos that was structured according to moral principles and significant numerical relationships and may have been akin to conceptions of the cosmos found in Platonic myths, such as those at the end of the Phaedo and Republic. In such a cosmos, the planets were seen as instruments of divine vengeance (“the hounds of Persephone”), the sun and moon are the isles of the blessed where we may go, if we live a good life, while thunder functioned to frighten the souls being punished in Tartarus. The heavenly bodies also appear to have moved in accordance with the mathematical ratios that govern the concordant musical intervals in order to produce a music of the heavens, which in the later tradition developed into “the harmony of the spheres.” It is doubtful that Pythagoras himself thought in terms of spheres, and the mathematics of the movements of the heavens was not worked out in detail. But there is evidence that he valued relationships between numbers such as those embodied in the so-called Pythagorean theorem, though it is not likely that he proved the theorem.Pythagoreanism, then, is a way of life, and both Plato and Aristotle refer to Pythagoras as a "founder of a way of life" (see Huffman's online article). In this way of life there is no separation between ethics and cosmology, just as there is no separation between the nature of the human soul and the nature of the Cosmos and the Gods. The ethical principles that human beings should strive to implement in our lives reflect the moral order that can be observed at work in the cosmos. And in the same way, the human soul internally mirrors the external order of the cosmos and, therefore, the fate of the soul is bound up with our progress in aligning our lives with the cosmic order.Pythagoras' cosmos was developed in a more scientific and mathematical direction by his successors in the Pythagorean tradition, Philolaus and Archytas. Pythagoras succeeded in promulgating a new more optimistic view of the fate of the soul after death and in founding a way of life that was attractive for its rigor and discipline and that drew to him numerous devoted followers.
Christoph Riedweg (a Professor of Classics at the University of Zurich and Director of the Swiss Institute in Rome) is another scholar of Pythagoreanism. His Pythagoras: His Life and Teachings is now available in English. Here is how it begins
A peculiar kind of splendor surrounds the name of Pythagoras of Samos -- a splendor probably due in no small measure to the fact that in his person enlightened modern science seems happily fused with ancient wisdom teachings and insights into the mysterious interconnections of the world. The first is presented by the Pythagorean Theorem that we all learn in school, a² + b² = c², ... as well as by Pythagoras' recognition of the mathematical character of the basic musical concords. The transfer of these musical proportions to the cosmos (the "harmony of the spheres") and the use of music for therapeutic ends, and the transmigration of souls are key terms for the second aspect. Pythagoras has a guaranteed place not only in musicology, mathematics, and the history of science but also in the history of philosophy and religion....Pythagoreanism's tight integration of the cosmological and the personal is very similar to the Indian conceptions of Rebirth and Karma, as can be seen in what the modern Hindu sage Sri Aurobindo says here:
The one question which through all its complexities is the sum of philosophy and to which all human enquiry comes round in the end, is the problem of ourselves, -- why we are here and what we are, and what is behind and before and around us, and what are we to do with ourselves, our inner significances and our outer environment. In the idea of evolutionary rebirth, if we can once find it to be a truth and recognize its antecedents and consequences, we have a very significant clue for an answer to all these connected sides of the one perpetual question. A spiritual evolution of which our universe is the scene and earth its ground and stage, though its plan is still kept back above from our yet limited knowledge, -- this way of seeing existence is a luminous key which we can fit into many doors of obscurity. But we have to look at it in the right focus, to get its true proportions and, especially, to see it in its spiritual significance more than in its mechanical process. The failure to do that rightly will involve us in much philosophical finessing, drive on this side or the other to exaggerated negations and leave our statement of it, however perfect may be its logic, yet unsatisfying and unconvincing to the total intelligence and the complex soul of humanity.Aurobindo is describing the Hindu concept of "evolutionary rebirth" which is remarkably similar to the Pythagorean concept of metempsychosis, the quintessential idea associated with the Pythagorean view of the "fate of the soul". The close kinship of Pythagorean metempsychosis with Hindu karma/rebirth is further demonstrated by the very practical dietary conclusion that both traditions reach: the ethical necessity of vegetarianism.
[Rebirth and Karma, pp. 35-6]
Writing half a millennium after Pythagoras, Ovid produced a poetic explication of metempsychosis and vegetarianism that is a monument to the impact of Pythagoreanism throughout Greco-Roman culture. In the concluding book of Ovid's Metamorphoses, Pythagoras himself appears after being introduced as
.... the firstAnd then Pythagoras himself begins to speak, and his very first words are
to speak against the use of animals
as human food, a practice he denounced
with learned but unheeded lips.
[Book XV, Allen Mandelbaum's translation is used throughout in the following.]
O mortals, don't contaminate your bodiesAfter a long and passionate exhortation to vegetarianism, Ovid's Pythagoras proclaims that "I'll reveal the truths of heaven, all the oracles that highest wisdom holds." Central to what Pythagoras now reveals is that
with food procured so sacrilegiously.
all things flow; all things are bornBut this is still just a very general statement about the constant state of becoming that is the essence of the physical universe. A little further on, Pythagoras/Ovid gets down to details:
to change their shapes. And time itself is like
a river, flowing on an endless course.
Witness: no stream and no swift movement can
relent; they must forever flow; just as
wave follows wave, and every wave is pressed,
and also presses on the wave ahead;
so, too, must moments always be renewed.
What was is now no more, and what was not
has come to be; renewal is the lot
of time.
Just so, our bodies undergoBut even this is only birth, not yet is there mention of rebirth. The poet/philosopher goes on to describe the arc of life from birth to old age, but then, at death's door as it were, he suddenly returns to the broader theme of impermanence in general -- as opposed to mere human mortality. Indeed, we are now told that "[n]ot even things we call the elements persist", and this serves as an introduction to a brief digression on the transformations of "earth, water, air, and fire". Pythagoras is obviously shifting back and forth between, on the one hand, the personal, individual experience of life, death and impermanence, and, on the other hand, the infinite dance of beginningless and never-ending transformations as seen from a cosmic perspective.
the never-resting changes: what we were
and what we are today is not to be
tomorrow. Once we were but simple seeds,
the germ from which -- one hoped -- a man might spring;
we dwelled within our mother's womb until,
with hands expert and wily, nature willed
that we not lie so cramped in narrow walls...
Having reminded us (of what we knew even before we were born, according to Plato's "doctrine" of anamnesis) that birth, death, and all other forms of transformation are not just our own personal fates, but the fate of all that is, Pythagoras reveals the connection between impermanence and immortality:
There is no thing that keeps its shape; for natureOvid's Pythagoras goes on (and on - remember, this was long before cable) stating and restating this strangely positive teaching of impermanence and immortality, but he eventually decides that perhaps he has finally succeeded in driving the point home, or that perhaps his audience is in danger of loosing sight of the forest for the trees:
the innovator, would forever draw
forms out of other forms. In all this world --
you can believe me -- no thing ever dies.
By birth we mean beginning to re-form,
a thing's becoming other than it was;
and death is but the end of the old state;
one thing shifts here, another there; and yet
the total of all things is permanent.
I think there's nothing that retains its form
for long: the world itself has undergone
the passage from the age of gold to iron.
And places also change: for I have seen
what once was solid land turn into sea,
and what before was sea turn into land.
Seashells lie distant from the oceanside;
old anchors have been found on mountain tops,
and waters flowing down the slopes have made
plains into valleys; and the force of floods
has carried mountains down into the sea;
what once were marshlands have become dry sands,
and lands that once were parched are now wet marsh.
Here nature has new fountains flow, and here
she blocks their course; the tremors of the earth
at times make rivers rush, at times obstruct
and curb a stream until it's seen no more.
The Lycus, swallowed by the yawning earth,
emerges at a point far off, reborn
in other guise; the Erasinus' flow
is swallowed by the soil and glides along
beneath the earth until it surfaces --
a mighty stream -- in the Argolic fields;
and, discontent with its old banks and source,
in Mysia the Caicus changed its course;
whereas the Amenanus, bearing sands,
at times will flow through Sicily and then,
at other time -- its sources blocked -- dries up.
But lest I gallop far beyond my reachAnd so finally the connection between metempsychosis and vegetarianism is laid out in no uncertain terms. Thyestes, of course, was famously tricked into eating the cooked flesh of his own sons. And the fact that he did not realize this at the time made it no less horrific when he discovered the truth (as we all inevitably must)!
and, so, forget what I had meant to teach,
know this: the heavens and all things beneath
the heavens change their forms -- the earth and all
that is upon the earth; and since we are
parts of the world, we, too, are changeable.
For we're not only bodies but winged souls;
and we can dwell in bodies of wild beasts
and hide within the shapes of cows and sheep.
And so, let us respect -- leave whole, intact --
all bodies where our parents' souls or those
of brothers or of others dear to us
may well have found a home; let us not stuff
our bellies banqueting, as Thyestes.
Addenda
1. To learn more about Pythagoreanism in general, in addition to Riedweg's book mentioned above also check out The Pythagorean Sourcebook and Library by Kenneth Sylvan Guthrie and David Fideler, and also Charles Kahn's Pythagoras and Pythagoreanism: A Brief History.
2. The striking image at the very top of this post is from the cover of Mary Zimmerman's 2002 Metamorphoses: A Play. Zimmerman's theatrical adaptation actually doesn't mention either Pythagoras or King Numa, the person being addressed by Pythagoras (although they were both, naturally, included in all their Ovidian glory in the complete free-verse translation by David R. Slavitt, which was the basis for Zimmerman's play). However, Zimmerman did insert the story of Eros and Psyche, which is not in Ovid at all but is rather from our old friend Apuleius of Madaurus! And of course Apuleius' book, from which the story of Eros and Psyche was taken, was also titled Metmorphoses (the story is found in Books Four, Five and Six). When asked why she put Eros and Psyche in the play Zimmerman's very reasonable explanation was simply that "I love it [Apuleius' Eros and Psyche] so much I just had to put it in." As far as I know no one has asked why she took Pythagoras and King Numa out, but I suspect that a long harangue on vegetarianism was not what she had in mind for the play's ending.