GEOMETRY:PHILOSOPHICAL ASPECTS
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such deductive systems would be deterministic;
there would quite literally be “no new thing under
the sun” (Eccles. 1:9). At best, as occurs when im-
plicit truths are rendered explicit by the articulation
and proof of a new theorem in geometry, people
would find themselves surprised by the unfore-
seen; but any freedom, either for God or for
human beings, would be illusory, the outworking
of an implicit and inevitable necessity.
Since Kant, people have been forced to take
seriously the notion that what they regard as the
intelligibility of the world is in reality the inner co-
herence of their modes of thought: in Vico’s lan-
guage, the intelligibility of the made, not the
found. Objections to the employment of geometry
as a model for the world reiterate this view in the
context of doubts about the fine structure of the
world and the limits of observation. Such doubts
have been reinforced by the development of quan-
tum mechanics and relativity, which suggest that
human intuitions about the world are mistaken (al-
though even these suggestions are still to be con-
strued within a conceptual system, and not as
grounded in a noumenal world).
Nonetheless, the expansion of elementary
geometry into analytic geometry, topology, and
linear algebra, preserves the sense of the “unrea-
sonable effectiveness of mathematics,” and sug-
gests that, all doubts to the contrary notwithstand-
ing, there may remain some sense in Newton’s
designation of the universe as the divine senso-
rium, albeit construed as a creation embodying the
structure of a divine geometry, and intelligible only
to a divine mind.
John Stuart Mill (1806–1873) was one of the
first to challenge Kant’s view that the a priori truths
of geometry are necessary consequences of the
possibility conditions of rational thought, in other
words, that to be rational people have to think the
world, amongst other things, in Euclidean terms.
Mill did not know of non-Euclidean geometry, but
attributed the apparent inescapability of Euclidean
geometry to paucity of imagination, and its domi-
nation to the kinds of experiences to which human
beings are susceptible. Mill seems to have been
vindicated by the predilection of physical theory—
in both quantum mechanics and relativity—for
non-Euclidean geometries that defy everyday
human intuitions.
Towards the end of the nineteenth century
fundamental changes in philosophy of mathemat-
ics occurred, most notably the articulation of logi-
cism by German mathematician and philosopher
Gottlob Frege (1848–1925). Frege attempted to re-
duce arithmetic to logical categories by employing
the theory of sets and the non-Euclidean geome-
tries of Riemann that discard the intuitive notions
of line and plane familiar from Euclid in favor of
abstract n-tuples governed by arbitrary rules.
Attempts to reduce mathematics to logic were
associated with Frege’s attack on psychologism, it-
self a descendant of Kant’s view that the nature of
intelligible reality is governed not by properties of
an objective world but by the rules of thought.
Often called a modern platonism, Frege’s work
struggled to ground mathematics in an inviolable
world independent of experience. Unfortunately,
by adopting the theory of sets, Frege fell foul of
Bertrand Russell’s (1872–1970) celebrated paradox
that the “set of all sets that are not members of
themselves” both is and is not a member of itself,
thus demonstrating that there is an apparent antin-
omy in the theory of sets.
Quite apart from its relevance to ontology and
epistemology, and thus to theology, geometry has
played a major role in the more everyday devel-
opment of religion. Closely associated with the ed-
ucated and priestly classes, with astronomy and
astrology, with numerology and mysticism, geom-
etry has repeatedly had an impact on the way peo-
ple have viewed the order and mystery of the
world. The Pythagoreans regarded number as the
basis of all knowledge and truth, many religions
and cults have seen mystical significance in the
properties of geometrical shapes, especially the
golden rectangle/ratio and the pentangle, widely
employed in magic.
The fundamental religious importance of
geometry nevertheless emerges from questions of
the relationship between divine creative purpose,
the structure and operation of the natural world,
and the conceptual capacities of the human mind.
If, as Einstein suggested, “the only unintelligible
thing about the world is that it is intelligible,” there
seems to be an intrinsic harmony between all three,
and geometry seems able, at least in the limit, to
embody the structure of the world as found. If, as
others suggest, following Kant, “the only intelligible
thing about the world is that it is unintelligible,”