Ithaca takes the form of a catechism, the Q&A
dialogue by which Catholic schoolchildren are indoctrinated in
the faith. (Joyce had to memorize two of them before his 10th
birthday.) But rather than using theology to explain the ways
of God, this one uses science to explain the ways of the
natural world. Joyce once called it "a mathematical
catechism." Not all of its hyper-rationalistic questions and
answers evoke scientific inquiry, but many do. The first pair
sets the tone by using geometry to describe the "parallel
courses" which Stephen and Bloom take to Bloom's house,
including a "diametrical" passage through the center of a
circle.
The schema that Joyce gave to Stuart Gilbert lists
"Cathechism (impersonal)" as the technique of Ithaca,
and "Science" as its art. The art of geometry is applied to
the route that the two men follow on their way from the
cabman's shelter to Bloom's house. Their paths are called "parallel
courses"—a strangely abstract way of describing the
perfectly ordinary phenomenon of two people walking this way
and that, but always at about the same distance from one
another. Similarly, at the end of the paragraph, the perfectly
ordinary experience of cutting across the interior of a
circular path to shave off distance is laid out schematically
as a geometry problem: "they crossed both the circus
before George's church diametrically, the chord in any
circle being less than the arc which it subtends."
A mathematician would say, as the physicist on the Rutgers
website cited here does, that "As A becomes smaller, the chord
length d becomes a better approximation to the arc length d',
that is, d ~ d'." And, conversely, as angle A increases, the
ratio of d to d' falls further away from 1/1. When the angle
is maximized at 180 degrees, chord d = D x 2, while arc d' = D
x ~3.14, for a ratio of less than 2/3––a significant reduction
for two tired walkers. Stephen and Bloom save energy in this
way by crossing the "circus" in front of St. George's
church "diametrically." Joyce has chosen both
words carefully. The Latin word circus means simply
circle. (In British usage it refers to an open circular plaza
where streets converge.) The diameter traced by the two men's
feet is the straight line through the center of this circle.
Readers who find such hyper-precise language arcane, tedious,
or irrelevant to the conduct of life may initially be put off
by Ithaca. But they will find its questions and
answers far more playful, adventurous, and liberating than
those of The Maynooth Catechism. And, for some
modern readers at least, the subjects covered in the chapter
will seem more relevant to the problems of life than learning
how many angels can dance on the head of a pin.
