The Sleepwalkers (48 page)

The
renaissance
of
learning
in
the
thirteenth
century
was
full
of
promise
–
the
stirrings
of
a
patient
who
emerges
from
a
long,
comatose
state.
It
was
the
century
of
Robert
of
Lincoln
and
Roger
Bacon,
the
first
who
understood,
far
ahead
of
his
time,
the
principles
and
methods
of
empirical
science;
of
Peter
Peregrine,
who
wrote
the
first
scientific
treatise
on
the
magnetic
compass,
and
of
Albert
the
Great,
the
first
serious
naturalist
since
the
Plinys,
who
studied
insects,
whales
and
polar
bears,
and
gave
a
fairly
complete
description
of
German
mammals
and
birds.
The
young
universities
of
Salerno
and
Bologna,
of
Paris,
Oxford
and
Cambridge,
radiated
the
new
fervour
of
learning
which
had
brought
on
the
thaw.

2.
Potency and Act

And
yet
after
these
great
and
hopeful
stirrings,
the
philosophy
of
nature
gradually
froze
up
again
in
scholastic
rigidity
–
though
not
entirely
this
time.
The
reason
for
this
short
splendour
and
long
decline
can
be
summed
up
in
a
single
phrase:
the
rediscovery
of
Aristotle
had
changed
the
intellectual
climate
of
Europe
by
encouraging
the
study
of
nature;
the
concrete
teachings
of
Aristotelian
science,
elevated
into
dogmas,
paralysed
the
study
of
nature.
If
the
schoolmen
had
merely
listened
to
the
cheerful
and
encouraging
timbre
in
the
Stagyrite's
voice,
all
would
have
been
well;
but
they
made
the
mistake
of
taking
in
what
it
actually
said
–
and
insofar
as
the
physical
sciences
are
concerned,
what
it
said
was
pure
rubbish.
Yet
for
the
next
three
hundred
years
this
rubbish
came
to
be
regarded
as
gospel
truth.
⁴

I
must
now
say
a
few
words
about
Aristotelian
physics,
for
it
is
an
essential
part
of
the
medieval
universe.
The
Pythagoreans
had
shown
that
the
pitch
of
a
tone
depends
on
the
length
of
a
cord,
and
had
thus
pointed
the
way
to
the
mathematical
treatment
of
physics.
Aristotle
divorced
science
from
mathematics.
To
the
modern
mind,
the
most
striking
fact
about
medieval
science
is
that
it
ignores
numbers,
weight,
length,
speed,
duration,
quantity.
Instead
of
proceeding
by
observation
and
measurement,
as
the
Pythagoreans
did,
Aristotle
constructed,
by
that
method
of
a
priori
reasoning
which
he
so
eloquently
condemned,
a
weird
system
of
physics
"argued
from
notions
and
not
from
facts".
Borrowing
his
ideas
from
his
favourite
science,
biology,
he
attributed
to
all
inanimate
objects
a
purposeful
striving
toward
an
end,
which
is
defined
by
the
inherent
nature
or
essence
of
the
thing.
A
stone,
for
instance,
is
of
an
earthly
nature,
and
while
it
falls
toward
the
centre
of
the
earth
it
will
increase
its
speed,
because
of
its
impatience
to
get
"home";
and
a
flame
will
strive
upward
because
its
home
is
in
the
sky.
Thus
all
motion,
and
all
change
in
general,
is
the
realization
of
what
exists
potentially
in
the
nature
of
the
thing:
it
is
a
transition
from
"potency"
to
"act".
But
this
transition
can
only
be
achieved
with
the
help
of
some
other
agent
which
itself
is
in
the
"act";
⁵
thus
wood
which
is
potentially
hot,
can
be
made
actually
hot
only
by
fire,
which
is
actually
hot.
Similarly,
an
object
moving
from
A
to
B,
being
"in
a
state
of
potency
with
respect
to
B",
can
only
reach
B
with
the
help
of
an
active
mover
:
"whatever
is
moved
must
be
moved
by
another."
All
this
terrifying
verbal
acrobacy
can
be
summed
up
in
the
statement
that
things
only
move
when
they
are
pushed
–
which
is
as
simple
as
it
is
untrue.

Indeed,
Aristotle's
omne
quod
movetur
ab
alio
movetur
–
whatever
is
moved
must
be
moved
by
another
–
became
the
main
obstacle
to
the
progress
of
science
in
the
Middle
Ages.
The
idea
that
things
only
move
when
they
are
pushed
seems,
as
a
modern
scholar
remarks,
⁶
to
have
originated
with
the
painful
motion
of
oxcarts
over
bad
Grecian
roads,
where
friction
was
so
great
that
it
annihilated
momentum.
But
the
Greeks
also
shot
arrows,
threw
the
discus
and
spears
–
and
yet
chose
to
ignore
the
fact
that
once
the
initial
impulse
had
been
imparted
to
the
arrow,
it
continued
its
motion,
without
being
pushed,
until
gravity
brought
it
to
an
end.
According
to
Aristotelian
physics,
the
arrow,
the
moment
it
ceased
to
have
contact
with
its
mover,
the
bowstring,
ought
to
have
fallen
to
the
earth.
To
this
the
Aristotelians
gave
the
answer
that
when
the
arrow
started
moving
while
still
pushed
by
the
bow,
it
created
a
disturbance
in
the
air,
a
kind
of
vortex,
which
kept
dragging
it
along
its
course.
Not
before
the
fourteenth
century,
not
for
seventeen
hundred
years,
was
the
objection
raised
that
the
air-commotion
caused
by
the
arrow's
start
could
not
be
strong
enough
to
make
it
continue
its
flight
against
the
wind;
and
furthermore
that
if
a
boat,
kicked
away
from
the
shore,
continued
to
move
merely
because
it
was
pulled
along
by
the
commotion
in
the
water
which
the
boat
itself
had
caused,
then
the
initial
kick
should
be
sufficient
to
make
it
traverse
the
ocean.