The Sleepwalkers (190 page)

The
exact
circumstances
of
the
discovery
of
the
Third
Law
were
again
faithfully
recorded
by
Kepler:

"On
March
8
of
this
present
year
1618,
if
precise
dates
are
wanted,
[the
solution]
turned
up
in
my
head.
But
I
had
an
unlucky
hand
and
when
I
tested
it
by
computations
I
rejected
it
as
false.
In
the
end
it
came
back
again
to
me
on
May
15,
and
in
a
new
attack
conquered
the
darkness
of
my
mind;
it
agreed
so
perfectly
with
the
data
which
my
seventeen
years
of
labour
on
Tycho's
observations
had
yielded,
that
I
thought
at
first
I
was
dreaming,
or
that
I
had
committed
a
petitio
principi
..."
²¹

He
celebrated
his
new
discovery,
as
he
had
celebrated
his
First
Law,
with
a
quotation
from
Virgil's
E
clogues
;
in
both
cases
Truth
appears
in
the
shape
of
a
teasing
hussy
who
surrenders
unexpectedly
to
her
pursuer
when
he
has
already
given
up
hope.
And
in
both
cases
also,
the
true
solution
was
rejected
by
Kepler
when
it
first
occurred
to
him,
and
was
only
accepted
when
it
crept
in
a
second
time,
"through
a
back-door
of
the
mind".

He
had
been
searching
for
this
Third
Law,
that
is
to
say,
for
a
correlation
between
a
planet's
period
and
its
distance
,
since
his
youth.
Without
such
a
correlation,
the
universe
would
make
no
sense
to
him;
it
would
be
an
arbitrary
structure.
If
the
sun
had
the
power
to
govern
the
planets'
motions,
then
that
motion
must
somehow
depend
on
their
distance
from
the
sun;
but
how?
Kepler
was
the
first
who
saw
the
problem
–
quite
apart
from
the
fact
that
he
found
the
answer
to
it,
after
twenty-two
years
of
labour.
The
reason
why
nobody
before
him
had
asked
the
question
is
that
nobody
had
thought
of
cosmological
problems
in
terms
of
actual
physical
forces.
So
long
as
cosmology
remained
divorced
from
physical
causation
in
the
mind,
the
right
question
could
not
occur
in
that
mind.
Again
a
parallel
to
the
present
situation
imposes
itself:
there
is,
one
suspects,
a
fragmentation
in
the
twentieth
century
mind
which
prevents
it
from
asking
the
right
questions.
The
offspring
of
a
new
synthesis
is
not
a
ready
solution,
but
a
healthy
problem
crying
lustily
for
an
answer.
And
vice
versa
:
a
one-sided
philosophy
–
whether
it
be
scholasticism
or
nineteenth-century
mechanism,
creates
sick
problems,
of
the
sort
"What
is
the
sex
of
the
angels?"
or
"Is
man
a
machine?"

7.
The Ultimate Paradox

The
objective
importance
of
the
Third
Law
is
that
it
provided
the
final
clue
for
Newton;
hidden
away
in
it
is
the
essence
of
the
Law
of
Gravity.
But
its
subjective
importance
to
Kepler
was
that
it
furthered
his
chimerical
quest
–
and
nothing
else.
The
Law
makes
its
first
appearance
as
"Proposition
No.
8"
in
a
chapter
characteristically
called
"The
Main
Propositions
of
Astronomy
which
are
needed
for
the
Investigation
of
the
Celestial
Harmonies".
In
the
same
chapter
(the
only
one
in
the
book
which
deals
with
astronomy
proper)
the
First
Law
is
merely
mentioned
in
passing,
almost
shamefacedly,
and
the
Second
Law
not
at
all.
In
its
place
Kepler
once
more
quoted
his
faulty
inverse
ratio
proposition,
whose
incorrectness
he
once
knew
and
then
forgot.
Not
the
least
achievement
of
Newton
was
to
spot
the
Three
Laws
in
Kepler's
writings,
hidden
away
as
they
were
like
forget-me-nots
in
a
tropical
flowerbed.

To
change
metaphors
once
more:
the
three
Laws
are
the
pillars
on
which
the
edifice
of
modern
cosmology
rests;
but
to
Kepler
they
meant
no
more
than
bricks
among
other
bricks
for
the
construction
of
his
baroque
temple,
designed
by
a
moonstruck
architect.
He
never
realized
their
real
importance.
In
his
earliest
book
he
had
remarked
that
"Copernicus
did
not
know
how
rich
he
was";
the
same
remark
applies
to
Kepler
himself.

I
have
stressed
this
paradox
over
and
again;
now
it
is
time
to
try
to
resolve
it.
Firstly,
Kepler's
obsession
with
a
cosmos
built
around
the
Pythagorean
solids
and
the
musical
harmonies,
was
not
quite
as
extravagant
as
it
seems
to
us.
It
was
in
keeping
with
the
traditions
of
Neoplatonism,
with
the
revival
of
Pythagoreanism,
with
the
teaching
of
Paracelsians,
Rosicrucians,
astrologers,
alchemists,
cabbalists
and
hermetists,
who
were
still
conspicuously
in
evidence
in
the
early
seventeenth
century.
When
we
talk
of
"the
age
of
Kepler
and
Galileo",
we
are
apt
to
forget
that
they
were
isolated
individuals,
a
generation
ahead
of
the
most
enlightened
men
of
their
time.
If
the
"harmony
of
the
world"
was
a
fantastic
dream,
its
symbols
had
been
shared
by
a
whole
dreaming
culture.
If
it
was
an
idée
fixe
,
it
was
derived
from
a
collective
obsession
–
only
more
elaborate
and
precise,
enlarged
on
a
grandiose
scale,
more
artful
and
self-consistent,
carried
to
the
ultimate
perfection
of
mathematical
detail.
The
Keplerian
cosmos
is
the
crowning
achievement
of
a
type
of
cosmic
architecture
which
began
with
the
Babylonians
and
ends
with
Kepler
himself.