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Overlooking mathematical justifications in the Sanskrit tradition the nuanced case of G F W Thibaut

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Overlooking mathematical justifications in the Sanskrit tradition the nuanced case of G F W Thibaut
6
Overlooking mathematical justifications
in the Sanskrit tradition: the nuanced case
of G. F. W. Thibaut
Agat h e Kell e r
Introduction
Until the 1990s, the historiography of Indian mathematics largely held that
Indians did not use ‘proofs’ in their mathematical texts.1 Dhruv Raina has
shown that this interpretation arose partly from the fact that during the
second half of the nineteenth century, the French mathematicians who
analysed Indian astronomical and mathematical texts considered geometry
to be the measure of mathematical activity.2 The French mathematicians
relied on the work of the English philologers of the previous generation,
who considered the computational reasonings and algorithmic verifications merely ‘practical’ and devoid of the rigour and prestige of a real logical
and geometrical demonstration. Against this historiographical backdrop,
the German philologer Georg Friedrich Wilhelm Thibaut (1848–1914)
published the oldest known mathematical texts in Sanskrit, which are
devoted only to geometry.
These texts, śulbasūtras (sometimes called the sulvasūtras) contain
treatises by different authors (Baudhāyana, Āpastamba, Kātyāyana and
Mānava) and consider the geometry of the Vedic altar.3 These texts were
written in the style typical of aphoristic sūtras between 600 and 200 bce.
They were sometimes accompanied by later commentaries, the earliest
of which may be assigned to roughly the thirteenth century. In order
to understand the methods that he openly employed for this corpus of
texts, Thibaut must be situated as a scholar. This analysis will focus on
Thibaut’s historiography of mathematics, especially on his perception
of mathematical justifications.
1
2
3
260
Srinivas 1990; H1995.
See Raina 1999: chapter vi.
I will adopt the usual transliteration of Sanskrit words, which will be marked in italics, except
for the word Veda, which is found in English dictionaries.
The Sanskrit tradition: the case of G. F. W. Thibaut
Thibaut’s intellectual background
Thibaut’s approach to the śulbasūtras combines what half a century before
him had been two conflicting traditions. As described by Raina and by
Charette, Thibaut was equal parts acute philologer and scientist investigating the history of mathematics.
A philologer
Thibaut trained according to the German model of a Sanskritist.4 Born in
1848 in Heidelberg, he studied Indology in Germany. His European career
culminated when he left for England in 1870 to work as an assistant for Max
Müller’s edition of the Vedas. In 1875, he became Professor of Sanskrit at
Benares Sanskrit College. At this time, he produced his edition and studies
of the śulbasūtras, the focus of the present article.5 Afterwards, Thibaut
spent the following twenty years in India, teaching Sanskrit, publishing
translations and editing numerous texts. With P. Griffith, he was responsible for the Benares Sanskrit Series, from 1880 onwards. As a specialist
in the study of the ritualistic mimām.sa school of philosophy and Sanskrit
scholarly grammar, Thibaut made regular incursions into the history of
mathematics and astronomy.
Thibaut’s interest in mathematics and astronomy in part derives from his
interest in mimām.sa. The authors of this school commented upon the ancillary parts of the Vedas (vedāṅga) devoted to ritual. The śulbasūtras can be
found in this auxiliary literature on the Vedas. As a result of having studied
these texts, between 1875 and 1878,6 Thibaut published several articles
on Vedic mathematics and astronomy. These studies sparked his curiosity about the later traditions of astronomy and mathematics in the Indian
subcontinent and the first volume of the Benares Sanskrit Series, of which
Thibaut was the general scientific editor, was the Siddhāntatattvaviveka of
Bhat.t.a Kamalākara. This astronomical treatise written in the seventeenth
century in Benares attempts to synthesize the reworkings of theoretical
astronomy made by the astronomers under the patronage of Ulug Begh
with the traditional Hindu siddhāntas.7
Thibaut’s next direct contribution to the history of mathematics and
astronomy in India was a study on the medieval astronomical treatise the
4
5
6
7
The following paragraph rests mainly on Stache-Rosen 1990.
See Thibaut 1874, Thibaut 1875, Thibaut 1877a, Thibaut 1877b.
The last being a study of the jyotisavedāṅga, in Thibaut 1878.
˙
See Minkowski 2001 and CESS, vol. 2: 21.
261
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agathe keller
Pañcasiddhānta of Varāhamihira. In 1888, he also edited and translated this
treatise with S. Dvivedi and consequently entered into a heated debate with
H. Jacobi on the latter’s attempt to date the Veda on the basis of descriptions
of heavenly bodies in ancient texts. At the end of his life, Thibaut published
several syntheses of ancient Indian mathematics and astronomy.8 His main
oeuvre, was not in the field of history of science but a three-volume translation of one of the main mimām
. sa texts: Śaṅkarācārya’s commentary on the
Vedāntasūtras, published in the Sacred Books of the East, the series initiated
by his teacher Max Müller.9 Thibaut died in Berlin at the beginning of the
First World War, in October 1914.
Among the śulbasūtras, Thibaut focused on Baudhāyana (c. 600 bce)10
and Āpastamba’s texts, occasionally examining Kātyāyana’s śulbapariśis.t.a.
Thibaut noted the existence of the Mānavasulbasūtra but seems not to have
had access to it.11 For his discussion of the text, Thibaut used Dvārakānātha
Yajvan’s commentary on the Baudhāyana sulbasūtra and Rāma’s (f l. 1447/9)
commentary on Kātyāyana’s text.12 Thibaut also occasionally quotes
Kapardisvāmin’s (f l. before 1250) commentary of Āpastamba.13 Thibaut’s
introductory study of these texts shows that he was familiar with the extant
philological and historical literature on the subject of Indian mathematics
and astronomy. However, Thibaut does not refer directly to any other scholars. The only work he acknowledges directly is A. C. Burnell’s catalogue of
manuscripts.14 For instance, Thibaut quotes Colebrooke’s translation of
Līlāvatī but does not refer to the work explicitly.15 Thibaut also reveals some
general reading on the history of mathematics. For example, he implicitly
refers to a large history of attempts to square the circle, but his sources are
unknown.
His approach to the texts shows the importance he ascribed to acute
philological studies.16 Thibaut often emphasizes how important commentaries are for reading the treatises: ‘the sūtra-s themselves are of an
8
9
10
11
12
13
14
15
16
Thibaut 1899, Thibaut 1907.
Thibaut 1904.
Unless stated otherwise, all dates refer to the CESS. When no date is given, the CESS likewise
gives no date.
For general comments on these texts, see Bag and Sen 1983, in CESS, vol 1: 50; vol 2: 30;
vol 4: 252. For the portions of Dvārakānātha’s and Venkateśvara’s commentaries on
Baudhāyana’s treatise, see Delire 2002.
Thibaut 1875: 3.
Thibaut 1877: 75.
Thibaut 1875: 3.
Thibaut 1875: 61.
See for instance Thibaut 1874: 75–6 and his long discussions on the translations of vr.ddha.
The Sanskrit tradition: the case of G. F. W. Thibaut
enigmatical shortness . . . but the commentaries leave no doubt about the
real meaning’.17
The importance of the commentary is also underlined in his introduction of the Pañcasiddhānta: ‘Commentaries can be hardly done without in
the case of any Sanskrit astronomical work . . .’18
However, Thibaut also remarks that because they were composed much
later than the treatises, such commentaries should be taken with critical
distance:
Trustworthy guides as they are in the greater number of cases, their tendency of
sacrificing geometrical constructions to numerical calculation, their excessive
fondness, as it might be styled, of doing sums renders them sometimes entirely
misleading.19
Indeed, Thibaut illustrated some of the commentaries’ ‘mis-readings’
and devoted an entire paragraph of his 1875 article to this topic. Thibaut
explained that he had focused on commentaries to read the treatises but
disregarded what was evidently their own input into the texts. Thibaut’s
method of openly discarding the specific mathematical contents of commentaries is crucial here. Indeed, according to the best evidence, the
tradition of ‘discussions on the validity of procedures’ appears in only the
medieval and modern commentaries.20 True, the commentaries described
mathematics of a period different than the texts upon which they
commented. However, Thibaut valued his own reconstructions of the
śulbasūtras proofs more than the ones given by commentaries.
The quote given above shows how Thibaut implicitly values geometrical
reasoning over arithmetical arguments, a fact to which we will return later.
It is also possible that the omission of mathematical justifications from the
narrative of the history of mathematics in India concerns not only the conception of what counts as proof but also concerns the conception of what
counts as a mathematical text. For Thibaut, the only real mathematical text
was the treatise, and consequently commentaries were read for clarification
but not considered for the mathematics they put forward.
In contradiction to what has been underlined here, the same 1875
article sometimes included commentators’ procedures, precisely because
the method they give is ‘purely geometrical and perfectly satisfactory’.21
17
18
19
20
21
Thibaut 1874: 18.
Thibaut 1888: v.
Thibaut 1875: 61–2.
These are discussed, in a specific case, in the other chapter in this volume I have written; see
Chapter 14.
This concludes a description of how to transform a square into a rectangle as described by
.
Dvārakantha in Thibaut 1875: 27–8.
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agathe keller
Thus there was a discrepancy between Thibaut’s statements concerning his
methodology and his philological practice.
Thibaut’s conception of the Sanskrit scholarly tradition and texts is also
contradictory. He alternates between a vision of a homogeneous and a
historical Indian society and culture and the subtleties demanded by the
philological study of Sanskrit texts.
In 1884, as Principal of Benares Sanskrit College (a position to which he
had been appointed in 1879), Thibaut entered a heated debate with Bapu
Pramadadas Mitra, one of the Sanskrit tutors of the college, on the question of the methodology of scholarly Sanskrit pandits. Always respectful to
the pandits who helped him in his work, Thibaut always mentioned their
contributions in his publications. Nonetheless, Thibaut openly advocated a
‘Europeanization’ of Sanskrit studies in Benares and sparked a controversy
about the need for pandits to learn English and the history of linguistics
and literature. Thibaut despaired of an absence of historical perspective in
pandits’ reasonings – an absence which led them often to be too reverent
towards the past.22 Indeed, he often criticized commentators for reading
their own methods and practices into the text, regardless of the treatises’
original intentions. His concern for history then ought to have led him to
consider the different mathematical and astronomical texts as evidence of
an evolution.
However, although he was a promoter of history, this did not prevent him
from making his own sweeping generalizations on all the texts of the Hindu
tradition in astronomy and mathematics. He writes in the introduction of
the Pañcasiddhānta:
these works [astronomical treatises by Brahmagupta and Bhāskarācarya] claim
for themselves direct or derived infallibility, propound their doctrines in a calmly
dogmatic tone, and either pay no attention whatever to views diverging from their
own or else refer to such only occasionally, and mostly in the tone of contemptuous
depreciation.23
Through his belief in a contemptuous arrogance on the part of the
writers, Thibaut implicitly denies the treatises any claim for reasonable
mathematical justifications, as we will see later. Thibaut attributed part of
the clumsiness which he criticized to their old age:
22
23
See Dalmia 1996: 328–30.
Thibaut 1888: vii. I am setting aside here the fact that he argues in this introduction for a Greek
origin of Indian astronomy. The square brackets indicate the present author’s addenda for the
sake of clarity.
The Sanskrit tradition: the case of G. F. W. Thibaut
Besides the quaint and clumsy terminology often employed for the expression of
very simple operations (. . .) is another proof for the high antiquity of these rules
of the cord, and separates them by a wide gulf from the products of later Indian
science with their abstract and refined terms.24
After claiming that the treatises had a dogmatic nature, Thibaut extends
this to the whole of ‘Hindu literature’:
The astronomical writers . . . therein only exemplify a general mental tendency
which displays itself in almost every department of Hindu Literature; but mere
dogmatic assertion appears more than ordinarily misplaced in an exact science like
astronomy . . .25
Thibaut does not seem to struggle with definitions of science, mathematics or astronomy, nor does he discuss his competency as a philologer in
undertaking such a study. In fact, Thibaut clearly states that subtle philology is not required for mathematical texts. He thus writes at the beginning
of the Pañcasiddhānta:
texts of purely mathematical or astronomical contents may, without great disadvantages, be submitted to a much rougher and bolder treatment than texts of
other kinds. What interests us in these works, is almost exclusively their matter,
not either their general style or the particular words employed, and the peculiar
nature of the subject often enables us to restore with nearly absolute certainty
the general meaning of passages the single words of which are past trustworthy
emendation.26
This ‘rougher and bolder treatment’ is evident, for instance, in his philologically accurate but somewhat clumsy translation of technical vocabulary.
He thus translates dīrghacaturaśra (literally ‘oblong quadrilateral’) variously; it is at some times a ‘rectangular oblong’, and at others an ‘oblong’.27
The expression ‘rectangular oblong’ is quite strange. Indeed, if the purpose
is to underline the fact that it is elongated, then why repeat the idea? The
first of Thibaut’s translations seems to aim at expressing the fact that a
dīrghacaturaśra has right angles, but the idea of orthogonality is never
explicit in the Sanskrit works used here, or even in later literature. Thibaut’s
translation, then, is not literal but coloured by his own idea of what a
dīrghacaturaśra is. Similarly, he calls the rules and verses of the treatises, the
Sanskrit sūtras, ‘proposition(s)’, which gives a clue to what he expects of a
24
25
26
27
Thibaut 1875: 60.
Thibaut 1888: vii.
Thibaut 1888: v.
See for instance Thibaut 1875: 6.
265
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scientific text, and thus also an inkling about what kind of scientific text he
suspected spawned the śulbasūtras.
Thibaut’s historiography of science
For Thibaut, ‘true science’ did not have a practical bent. In this sense, the
science embodied in the śulbas, which he considered motivated by a practical religious purpose, is ‘primitive’:
The way in which the sūtrakāra-s [those who compose treatises] found the cases
enumerated above, must of course be imagined as a very primitive one. Nothing
in the sūtra-s [the aphorisms with which treatises are composed] would justify the
assumption that they were expert in long calculations.28
However, he considered the knowledge worthwhile especially because it
was geometrical:
It certainly is a matter of some interest to see the old ācārya-s [masters] attempting
to solve this problem [squaring of the circle], which has since haunted so m[an]y
unquiet minds. It is true the motives leading them to the investigation were vastly
different from those of their followers in this arduous task. Theirs was not the disinterested love of research which distinguishes true science, nor the inordinate craving
of undisciplined minds for the solution of riddles which reason tells us cannot be
solved; theirs was simply the earnest desire to render their sacrifice in all its particulars acceptable to the gods, and to deserve the boons which the gods confer in
return upon the faithful and conscientious worshipper.29
Or again:
. . . we must remember that they were interested in geometrical truths only as far as
they were of practical use, and that they accordingly gave to them the most practical
expression.30
Conversely, the practical aspect of these primitive mathematics explains
why the methods they used were geometrical:
It is true that the exclusively practical purpose of the Śulvasūtra-s necessitated
in some way the employment of practical, that means in this case, geometrical
terms, . . .31
28
29
30
31
Thibaut 1875: 17.
Thibaut 1875: 33. The emphasis is mine.
Thibaut 1875: 9.
Thibaut 1875: 61.
The Sanskrit tradition: the case of G. F. W. Thibaut
This geometrical basis distinguished the śulbasūtras from medieval or
classical Indian mathematical treatises. Once again, Thibaut took this occasion to show his preference for geometry over arithmetic:
Clumsy and ungainly as these old sūtra-s undoubtedly are, they have at least the
advantage of dealing with geometrical operations in really geometrical terms, and
are in this point superior to the treatment of geometrical questions which we find
in the Līlāvatī and similar works.32
As is made clear from the above quotation, Thibaut was a presentist historian of science who possessed a set of criteria which enabled him to judge
the contents and the form of ancient texts. In another striking instance,
Thibaut gives us a clue that Euclid is one of his references. Commenting on
rules to make a new square of which the area is the sum or the difference of
two known squares, Thibaut states in the middle of his own translation of
Baudhāyana’s śulbasūtras:
Concerning the methods, which the Śulvasūtras teach for caturasrasamāsa (sum of
squares) and caturasranirhāra (subtraction of squares), I will only remark that they
are perfectly legitimate; they are at the bottom the same which Euclid employs.33
Contemptuous as he may be of the state of Indian mathematics, Thibaut did
not believe that the śulbasūtras were influenced by Greek geometry.34
For Thibaut, history of mathematics ought to reconstruct the entire
deductive process from the origin of an idea to the way it was justified.
Although later commentaries may include some useful information, they
do not give us the key to understanding how these ideas were developed
at the time when the treatises were composed. This lack of information
provoked Thibaut to complain about Indian astronomical and mathematical texts.
Thibaut clearly considered the texts to have been arranged haphazardly
because the order of the rules do not obey generative logic. He thus defined
his task: ‘I shall extract and fully explain the most important sūtra-s (. . .)
and so try to exhibit in some systematic order the knowledge embodied in
these ancient sacrificial tracts.’35 Here, Thibaut assumed that these works –
not treatises but ‘tracts’ (presumably with derogatory connotations) – are
not clear and systematic. Further, Thibaut felt the need to disentangle
(‘extract’) the knowledge they contain.
32
33
34
35
Thibaut 1875: 60.
Thibaut 1877: 76. Translations within brackets are mine.
Thibaut 1875: 4. This however was still being discussed as late as Staal 1999.
Thibaut 1875: 5.
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In his view, this knowledge might be quite remarkable but it was ill pre.
sented. Thus commenting a couple years later on the Vedāngajyotis.a, he
remarked:
The first obstacle in our way is of course the style of the treatise itself with its enigmatical shortness of expression, its strange archaic forms and its utter want of connection between the single verses.36
He thus sometimes remarked where the rules should have been placed
according to his logic. All the various texts of the śulbasūtras start by
describing how to construct a square, particularly how to make a square
from a rectangle.
However, Thibaut objected: ‘their [the rules for making a square from a
rectangle] right place is here, after the general propositions about the diagonal of squares and oblongs, upon which they are founded’.37 Consequently,
Thibaut considered the śulbasūtras as a single general body of text and
selected the scattered pieces of the process he hoped to reconstruct from
among all the sūtras composed by various authors. At the same time, he distinguished the different authors of the śulbasūtras and repeatedly insisted
that Āpastamba is more ‘practical’ than Baudhāyana, whom he preferred.
For instance, an example of his method:
Baudhāyana does not give the numbers expressing the length of the diagonals of
his oblongs or the hypotenuses of the rectangular triangles, and I subjoin therefore
some rules from Āpastamba, which supply this want, while they show at the same
time the practical use, to which the knowledge embodied in Baudhāyana’s sūtra
could be turned.38
When alternating among several authors was insufficient for his purposes,
Thibaut supplied his own presuppositions.
Indeed, Thibaut peppered his text with such reconstructions:
The authors of the sūtra-s do not give us any hint as to the way in which they found
their proposition regarding the diagonal of a square; but we may suppose . . . The
question arises: how did Baudhāyana or Āpastamba or whoever may have the merit
of the first investigation, find this value? . . . I suppose that they arrived at their
result by the following method which accounts for the exact degree of accuracy they
reached . . . Baudhāyana does not state at the outset what the shape of his wheel will
be, but from the result of his rules we may conclude his intention . . .39
36
37
38
39
Thibaut 1877: 411; the emphasis is mine.
Thibaut 1875: 28.
Thibaut 1875: 12.
Thibaut 1875: 11, 18, 49.
The Sanskrit tradition: the case of G. F. W. Thibaut
Because he had an acute idea of what was logically necessary, Thibaut thus
had a clear idea of what was sufficient and insufficient for reconstructing
the processes. As a result, Thibaut did not deem the arithmetical reasoning
of Dvārakānātha adequate evidence of mathematical reasoning.
The misunderstandings on which Thibaut’s judgements rest are evident.
For him, astronomical and mathematical texts should be constructed
logically and clearly, with all propositions regularly demonstrated. This
presumption compelled him to overlook what he surely must have known
from his familiarity with Sanskrit scholarly texts: the elaborate character
of a sūtra – marked by the diverse readings that one can extract from it –
enjoyed a long Sanskrit philological tradition. In other words, when a
commentator extracts a new reading from one or several sūtras, he demonstrates the fruitfulness of the sūtras. The commentator does not aim to
retrieve a univocal singular meaning but on the contrary underline the
multiple readings the sūtra can generate. Additionally, as Thibaut rightly
underlined, geometrical reasoning represented no special landmark of
correctness in reasoning to medieval Indian authors.
Because of these expectations and misunderstandings Thibaut was
unable to find the mathematical justifications that maybe were in these
texts. Let us thus look more closely at the type of reconstruction that
Thibaut employed, particularly in the case of proofs.
Practices and readings in the history of science
It is telling that the word ‘proof ’ is used more often by Thibaut in relation
to philological reasonings than in relation to mathematics. Thus, as we have
seen above, the word is used to indicate that the clumsiness of the vocabulary establishes the śulbasūtras’ antiquity.
No mathematical justifications in the śulbasūtras
However, for Thibaut, Baudhāyana and probably other ‘abstractly bent’
treatise writers doubtlessly wanted to justify their procedures. More often
than not, these authors did not disclose their modes of justification. Thus,
when the authors are silent, Thibaut developed fictional historical procedures. For instance:
The authors of the sūtra-s do not give us any hint as to the way in which they
found their proposition regarding the diagonal of a square [e.g. the Pythagorean
proposition in a square]; but we may suppose that they, too, were observant of
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the fact that the square on the diagonal is divided by its own diagonals into four
triangles, one of which is equal to half the first square. This is at the same time an
immediately convincing proof of the Pythagorean proposition as far as squares
or equilateral rectangular triangles are concerned . . . But how did the sūtrakāra-s
[composers of treatises] satisfy themselves of the general truth of their second
proposition regarding the diagonal of rectangular oblongs? Here there was no such
simple diagram as that which demonstrates the truth of the proposition regarding
the diagonal of the square, and other means of proof had to be devised.40
Thibaut thus implied that diagrams were used to ‘show’ the reasoning
literally and thus ‘prove’ it. This method seems to hint that authors of the
medieval period of Sanskrit mathematics could have had some sort of geometrical justification.41 Concerning Āpastamba’s methods of constructing
fire altars, which was based on known Pythagorean triplets, Thibaut stated:
In this manner Āpastamba turns the Pythagorean triangles known to him to practical use . . . but after all Baudhāyana’s way of mentioning these triangles as proving
his proposition about the diagonal of an oblong is more judicious. It was no practical want which could have given the impulse to such a research [on how to measure
and construct the sides and diagonals of rectangles] – for right angles could be
drawn as soon as one of the vijñeya [determined] oblongs (for instance that of 3,
4, 5) was known – but the want of some mathematical justifications which might
establish a firm conviction of the truth of the proposition.42
So, in both cases, Thibaut represented the existence and knowledge of
several Pythagorean triplets as the result of not having any mathematical
justification for the Pythagorean Theorem. Thibaut proceeded to use this
fact as a criterion by which to judge both Āpastamba’s and Baudhāyana’s
use of Pythagorean triplets. Thibaut’s search for an appropriate geometrical
mathematical justification in the śulbasūtras may have made him overlook
a striking phenomenon.
Two different rules for the same result
Indeed, Thibaut underlined that several algorithms are occasionally given
in order to obtain the same result. This redundancy puzzled him at times.
40
41
42
Thibaut 1875: 11–12.
See Keller 2005. Bhāskara’s commentary on the Āryabhat.īya was not published during
Thibaut’s lifetime, but I sometimes suspect that either he or a pandit with whom he worked had
read it. The discussion on vis.amacaturaśra and samacaturaśra, in Thibaut 1875: 10, thus echoes
Bhāskara I’s discussion on verse 3 of Chapter 2 of the Āryabhat.īya. Thibaut’s conception of
geometrical proof is similar to Bhāskara’s as well.
Thibaut 1875: 17.
The Sanskrit tradition: the case of G. F. W. Thibaut
For instance, Thibaut examined the many various caturaśrakaran.a –
methods to construct a square – given by different authors.43 Āpastamba,
Baudhāyana and Kātyāyana each gave two methods to accomplish this
task. I will not expound these methods here; they have been explained
amply and clearly elsewhere.44 Thibaut also remarked that in some cases,
Baudhāyana gives a rule and its reverse, although the reverse cannot be
grounded in geometry. Such is the case with the procedure to turn a circle
into a square:
Considering this rule closer, we find that it is nothing but the reverse of the rule
for turning a square into a circle. It is clear, however, that the steps taken according
to this latter rule could not be traced back by means of a geometrical construction,
for if we have a circle given to us, nothing indicates what part of the diameter is to
be taken as the atiśayat.r. tīya (i.e. the segment of the diameter which is outside of
the square).45
I am no specialist in śulba geometry and do not know if we should see the
doubling of procedures and inverting of procedures as some sort of ‘proofs’,
but at the very least they can be considered efforts to convince the reader
that the procedures were correct. The necessity within the śulbasūtras to
convince and to verify has often been noted in the secondary literature, but
has never fully or precisely studied.46 Thibaut, although puzzled by the fact,
never addressed this topic. Similarly, later historians of mathematics have
noted that commentators on the śulbasūtras sought to verify the procedures
while setting aside the idea of a regular demonstration in these texts. Thus
Delire notes that Dvārakānātha used arithmetical computations as an easy
method of verification (in this case of the Pythagorean Theorem).47 The use
of two separate procedures to arrive at the same result, as argued in another
chapter in this volume,48 could have been a way of mathematically verifying
the correctness of an algorithm – an interpretation that did not occur to
Thibaut.
43
44
45
46
47
48
Thibaut 1875: 28–30.
Thibaut 1875: 28–30; Bag and Sen 1983 in CESS, vol. 1; Datta 1993: 55–62; and finally Delire
2002: 75–7.
Thibaut 1875: 35.
See for instance Datta 1993: 50–1.
Delire 2002: 129.
See Keller, Chapter 14, this volume.
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agathe keller
Conclusion
Thibaut, as we have thus seen, embodied contradictions. On the one hand,
he swept aside the Sanskrit literary tradition and criticized its concise
sūtras as obscure, dogmatic and following no logic whatsoever. On the
other hand, as an acute philologer, he produced nuanced studies on the
differences among the approaches of different authors. Through his naive
assumption of a practical mind of the ‘Hindu astronomers’, his fruitless
search for proper visual demonstrations in an algorithmic tradition, and
a disregard of commentaries in favour of the treatises, Thibaut envisioned
a tradition of mathematics in India blind to the logic that could have been
used to justify the algorithms which he studied. Such arguments could
have been perceived through the case of the ‘doubled’ procedures in the
śulbasūtras, and maybe even through the arithmetical readings of these
geometrical texts found in later commentaries.
Acknowledgement
I would like to thank K. Chemla and M. Ross for their close reading of this
article. They have considerably helped in improving it.
Bibliography
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