Rhythm, Number, and Heraclitus’ River

David E. Cohen

The following short passage was recorded by an anonymous student of Aristotle or his school in the section on music in the pseudo-Aristotelian work known as the Problems:

We enjoy rhythm because it possesses number both familiar and ordered, and moves us in an orderly way. For ordered movement is by nature more akin [to us] than disordered, as indeed [it is itself] more natural.[1]

We enjoy rhythm, this tells us, in part because it “possesses number,” and in part because it moves us in a particular, “natural” way. The following is a reading of this passage as an invitation to situate some fundamental issues concerning rhythm in a historical context.

Let us begin with “rhythm” (rhythmos) itself. The word has a number of meanings in ancient Greek, including “measure, proportion or symmetry of parts.” In the present (musical) context, its use would have implied the application of those concepts to the proportional relationships of time durations specifically, manifested first in the long and short syllables of the Greek language, especially as these were exploited in verse, and then in the analogous temporal relations evidenced in the tones of melody and the bodily movements of dance.

Thus for an educated Greek of antiquity, to say that rhythm is a phenomenon of quantity, measure, and proportion would have been to state the obvious. But the word “number” (arithmos) implies a more specific claim, namely, that rhythm consists in “discrete” quantity, that is, a kind of quantity that is intrinsically “quantized,” coming in distinct, segregated units, or discrete batches of a common unit, this being precisely what was meant in ancient Greek by “number” in the specific and proper sense of the word: a countable collection of units.[2] And this idea of units of measure, whether conglomerated into a set or concatenated in a (temporal or spatial) series, reminds us that the durational relations of measure, proportion, and symmetry mentioned above all entail regularity or periodicity, the recurrence of a single, consistent time span. As we are told in an earlier section of the Problems, “every rhythm is measured by a determinate motion, and equal motion is of this kind.”[3]

All this implies that, for the writer and readers of our quoted passage, rhythm might have had a quality akin to that which we now call meter, characterized by periodicity, regularity, symmetry, the repetitive and predictable recurrence of identically “spaced” modules of identical “length.”[4]

On the other hand, it is also possible—though unlikely—that in the phrase “rhythm possesses number,” “number” is being used generically or metaphorically to denote “quantity” in general (to posón). If so, then it could be read so as to include continuous quantity, the kind of quantity found in the lines, planes, and solids of geometry, which the Greeks also called “magnitude” (megethos). Such a conception of the quantitative nature of rhythm might be taken to emphasize its continuity, its fluidity, its flow (rheuma). It might remind us that the word itself, rhythmos, is possibly related to the verb rhein, “to flow.” One might even go so far as to recall Heraclitus’s doctrine of universal flux: that “all things flow” (panta rhei) so that they are ever new, as in his saying that “upon those who step into the same rivers new waters are ever flowing.”[5] Such a reading would stress precisely those features that we now tend to associate specifically with rhythm: variety, creativity, unpredictability, what Christopher Hasty has characterized as the “spontaneous creation of the ever new,” in opposition to meter as the “constant repetition of the same.”[6]

That possibility is tempting. Nonetheless, the passage seems clearly to support the normal and proper meaning of “number” as “discrete quantity,” distinct groups of discrete units. For the passage goes on to characterize this “number” possessed by rhythm as both “familiar” and “ordered.” The word translated as “familiar” (gnôrimon) is from gnôrizein, “to come to know,” with its resonance of gnôsis, “knowledge,” suggesting that the “number” of rhythm is “familiar” in the sense of being “known” to the intellect, which recognizes something in it, meaning that the number in question is an entity of such a kind as to be, by nature, capable of being cognized (or “re-cognized”) by the mind; indeed its adverbial form gnôrimos means “intelligible,” “capable of being understood.” But for a Greek of the fourth century BC, that characterization would inevitably have implied the properties of regularity and finitude, as opposed to the chaotic and unknowable infinite.

At the same time, this “number” is ordered (tetagmenos); this word comes from a verb (tattein) that means to organize things or people into a definite arrangement, for example, to draw troops up into a battle formation; it is the same word that gives us “syntax” and its derivatives. It calls to mind the fact that another attested meaning of rhythmos is “form,” “shape.” And it is this property of being “ordered” that is responsible for rhythm’s powerful effect on us, which is to “move us in an orderly way” —something that rhythm can only do, of course, because it is already “ordered” itself, in a way that must somehow be related to the order that subsists in ourselves.

This is why our passage’s second sentence tells us that “ordered movement is by nature more akin [to us] than disordered, as indeed [it is itself] more natural”:  the word translated as “more akin,” oikeotera, characterizes things and people that are domestic, or related by blood, or friendly, or proper, or appropriate. Again, there is no fully satisfactory English equivalent, but all of those resonances amount to an implicit assertion of a profound and intimate relationship between us as living beings and the general phenomenon of “order.” We respond with pleasure to this phenomenon of order which, we are told, is also “more natural in itself,” because order is already within us as a principle of nature. And it is why the answer to the broader question of the passage as a whole, which asks why we take pleasure in melody and consonance as well as rhythm, is that we naturally enjoy those things that embody a proportion or ratio (logos), because “a ratio is [itself] an order (taxis); and order is, by nature, pleasant.”[7]

Measure, proportion, regularity, knowability, order: these properties would surely have seemed, to the early readers of this passage, far more characteristic of discrete quantities than of continuous ones, which—as had already long been known—are rife with the possibility of irrationality. (Think, for instance, of the value of pi.)

It is the fragmentary Elementa rhythmica of Aristoxenus, himself a student of Aristotle, that provides the earliest detailed theoretical account of rhythm in terms of proportional durational relations[8] —more specifically, of ratios between the durations of the upward motion (anô, arsis) and the downward motion (katô, basis) of the metrical verse foot, measured in multiples of a temporal unit he calls the prôtos chronos (the “primary duration”).[9] Rhythm, Aristoxenus says, occurs when the rhythmized material (speech in poetry, tones in music, movements in dance) is divided into parts that are, again, “knowable” (gnorimois), and so produce the special kind of determinate arrangement (taxis, from tattein) of temporal durations that qualifies as “rhythmic” (enrhythmon).[10] This requires (among other things) that the upward and downward motions of each foot be mutually commensurable: that each of them be an integral multiple of the protos chronos, which is therefore their “common measure” (metron koinon). Such a foot is “rational” (rhêtos). “Irrationality” (alogia) occurs when that is not the case. But this is not “irrationality” in the proper mathematical sense: it is not that the lengths of the arsis and basis have no possible “common unit.” Rather, Aristoxenus calls a foot “irrational” when the common measure of its up and down motions is a duration shorter than the perceptually indivisible protos chronos. Such a duration is, simply for that reason, “arrhythmic,” and all such irrational feet are “not proper (oikeiai) to the nature of rhythm” itself.[11] Consequently, only the very small set of verse feet with ratios that are, in this sense, “rational,” and are moreover “familiar” or “knowable” (gnôrimon) because their proportional relation of arsis to basis is easily perceptible, are “proper (oikeiai) to, and capable of being ordered in accord with, the nature of rhythm.”[12] All this, of course, rules out a fortiori any proportional relations that are truly irrational (in the proper mathematical sense of having no common unit at all), and so restricts the domain of rhythm to that of arithmos, “number” in the Greek sense explained earlier.

A few moments ago I mentioned Heraclitus’s maxim, “Upon those stepping into the same rivers ever new waters flow.” Unlike his other, more famous saying, “It is not possible to step into the same river twice,” or the catch phrase used to summarize his thought, “everything flows,” this one, which seems to acknowledge the sense in which people actually can “step into the same river” more than once, permits us to think that perhaps Heraclitus did recognize some sort of stability along with the flux. It prompts us to recognize that, while everything may be continually changing, it is precisely in and through that ceaseless alteration that the seemingly stable entities of our empirical world apparently persist and subsist. The parallels, and contrasts, with rhythm and meter are intriguing.

I’d like to close with the suggestion that this dialectic of flux and stasis, sameness and difference, unfolds not only over short spans but in and through the course of history as well. It is evident in our feeling that the anonymous Greek passage we’ve been examining says things that seem both archaic and alien, as in the emphasis on an otherwise undefined “number,” and on the other hand, things that seem quite current, such as its author’s unmistakable sense that within the phenomenon called “rhythm” and its powerful effect on us there is something that is both extraordinary and significant and yet deeply, intimately familiar. Rhythm does indeed move us, cause us pleasure, and, at least in many cases, seem profoundly natural while doing so. And we are still seeking to understand why, although the kinds of answers we prefer now are usually very different from those of over two thousand years ago. But what I especially like about the passage I’ve just been discussing is its quiet sense of wonder at the marvelous phenomenon of rhythm, and its calm confidence that this can be explained by being defined and situated within a world of nature that has not, as yet, been disenchanted. It is by studying the history of such questions and answers that one can sometimes come to a new understanding, not only of who we are, how we got here, and what we have gained, but also of what we have lost along the way.[13]


[1] ῥυθμῷ δὲ χαίρομεν διὰ τὸ γνώριμον καὶ τεταγμένον ἀριθμὸν ἔχειν, καὶ κινεῖν ἡμᾶς τεταγμένως· οἰκειοτέρα γὰρ ἡ τεταγμένη κίνησις φύσει τῆς ἀτάκτου, ὥστε καὶ κατὰ φύσιν μᾶλλον (Problemata, Book 19, Chap. 38; 920b33-36).

[2] The study that established the meaning of arithmos in ancient Greek mathematics is Jacob Klein, Greek Mathematical Thought and the Origin of Algebra, trans. Eva Brann (Cambridge, Mass.: M.I.T. Press, 1968), originally published in German in 1934.

[3] πᾶς ῥυθμὸς ὡρισμένῃ μετρεῖται κινήσει, τοιαύτη δ’ ἐστὶν ἡ δι’ ἴσου οὖσα (Problemata, Book 5, Chap. 16; 882b2-3).

[4] I draw here on the brilliant critique of this conception of meter by Christopher Hasty, Meter as Rhythm (Oxford & New York: Oxford University Press, 1997), esp. pp. 1-21.

[5] ποταμοῖσι τοῖσιν αὐτοῖσιν ἐμβαίνουσιν, ἕτερα καὶ ἕτερα ὕδατα ἐπιρρεῖ. (H. Diels and W. Kranz, eds., Die Fragmente der Vorsokratiker, 6th ed. (Berlin: Weidmann, 1951), Vol. 1, Chap. 22, Pt. B, Frag. 12).

[6] Hasty, op. cit., pp. 4-5.

[7] ὁ μὲν οὖν λόγος τάξις, ὃ ἦν φύσει ἡδύ (Problemata, Bk. 19, Chap. 38; 921a3-4).

[8] Aristoxenus’ Elementa rhythmica is well translated in Andrew Barker, Greek Musical Writings, Vol. 2 (Cambridge University Press, 1989). I quote here from the edition by G. B. Pighi (Bologna: Patron, 1959), as reproduced in Thesaurus Linguae Graecae (URL: stephanus.tlg.uci.edu).

[9] Aristoxenus defines the prôtos chronos as “that [duration] which cannot be divided” by the least division of any rhythmized material (speech sounds, musical tones, bodily motions): Καλείσθω δὲ πρῶτος μὲν τῶν χρόνων ὁ ὑπὸ μηδενὸς τῶν ῥυθμιζομένων δυνατὸς ὢν διαιρεθῆναι (ed. cit. p. 19:21-22). It is not, of course, indivisible in the absolute sense, since time itself for Aristotle and his followers is continuous.

[10] Ἀναγκαῖον οὖν ἂν εἴη μεριστὸν εἶναι τὸ ῥυθμιζόμενον γνωρίμοις μέρεσιν, οἷς διαιρήσει τὸν χρόνον. … Ἀκόλουθον δέ ἐστι … τὸ λέγειν, τὸν ῥυθμὸν γίνεσθαι, ὅταν ἡ τῶν χρόνων διαίρεσις τάξιν τινὰ λάβῃ ἀφωρισμένην, οὐ γὰρ πᾶσα χρόνων τάξις ἔνρυθμος (Elementa rhythmica, ed. cit., p. 18: 15-16, 18-20).

[11] Δεῖ δὲ μηδ’ ἐνταῦθα διαμαρτεῖν, ἀγνοηθέντος τοῦ τε ῥητοῦ καὶ τοῦ ἀλόγου, τίνα τρόπον ἐν τοῖς περὶ τοὺς ῥυθμοὺς λαμβάνεται. … Τὸ μὲν γὰρ κατὰ τὴν τοῦ ῥυθμοῦ φύσιν λαμβάνεται ῥητόν, τὸ δὲ κατὰ τοὺς τῶν ἀριθμῶν μόνον λόγους. Τὸ μὲν οὖν ἐν ῥυθμῷ λαμβανόμενον ῥητὸν χρόνου μέγεθος πρῶτον μὲν δεῖ τῶν πιπτόντων εἰς τὴν ῥυθμοποιίαν εἶναι, ἔπειτα τοῦ ποδὸς ἐν ᾧ τέτακται μέρος εἶναι ῥητόν· τὸ δὲ κατὰ τοὺς τῶν ἀριθμῶν λόγους λαμβανόμενον ῥητὸν τοιοῦτόν τι δεῖ νοεῖν οἷον ἐν τοῖς διαστηματικοῖς τὸ δωδεκατημόριον τοῦ τόνου καὶ εἴ τι τοιοῦτον ἄλλο ἐν ταῖς τῶν διαστημάτων παραλλαγαῖς λαμβάνεται. Φανερὸν δὲ διὰ τῶν εἰρημένων, ὅτι ἡ μέση ληφθεῖσα τῶν ἄρσεων οὐκ ἔσται σύμμετρος τῇ βάσει· οὐδὲν γὰρ αὐτῶν μέτρον ἐστὶ κοινὸν ἔνρυθμον (Elementa rhythmica, ed. cit., p. 23:1-3, 9-19).

[12] Διὰ ταύτην γὰρ τὴν αἰτίαν τὸ μὲν ἡρμοσμένον εἰς πολὺ ἐλάττους ἰδέας τίθεται, τὸ δὲ ἀνάρμοστον εἰς πολὺ πλείους. Οὕτω δὲ καὶ τὰ περὶ τοὺς χρόνους ἔχοντα φανήσεται· πολλαὶ μὲν γὰρ αὐτῶν συμμετρίαι τε καὶ τάξεις ἀλλότριαι φαίνονται τῆς αἰσθήσεως οὖσαι, ὀλίγαι δέ τινες οἰκεῖαί τε καὶ δυναταὶ ταχθῆναι εἰς τὴν τοῦ ῥυθμοῦ φύσιν (Elementa rhythmica, ed. cit., p. 19:3-8).

[13] The foregoing is an expanded and much revised version of remarks read at the opening plenary session of the fifth annual Mannes Institute for Advanced Studies in Music Theory, held at the Mannes School of Music in New York City in the summer of 2005. The Institute’s topic that year was rhythm, and I was to lead a workshop that would examine theories of rhythm historically. Each workshop leader delivered a brief preliminary address. I wish to thank Carmel Raz for suggesting that I share mine with the readers of the AMS / SMT HoT blog.


David E. Cohen is Senior Research Scientist with the research group, “Histories of Music, Mind, and Body” at the Max Planck Institute for Empirical Aesthetics in Frankfurt, Germany. His research focuses on the history of music theory from Greek antiquity through the nineteenth century. A PhD graduate of Brandeis University (1993), he has held professorships at Columbia, Harvard, and Tufts Universities, and visiting professorships at Yale and McGill Universities. His article, “‘The Imperfect Seeks its Perfection’: Harmonic Progression, Directed Motion, and Aristotelian Physics” received the 2001 Best Publication award of the Society for Music Theory. Among his current projects are an essay about the musical note as the “element” of music, a study on Rameau’s harmonic theory, and a book, The End of Pythagoreanism: Music Theory, Philosophy, and Science from the Middle Ages to the Enlightenment.


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