DOC. 42 SPECIAL AND GENERAL RELATIVITY 249
Part I
The
Special Theory
of
Relativity
ONE
Physical Meaning
of
Geometrical
Propositions
In
your schooldays most
of
you
who read this book made
acquaintance
with
the
noble
building
of
Euclid's
geome-
try,
and
you
remember-perhaps
with
more
respect
than
love-the
magnificent
structure,
on
the
lofty
staircase
of
which
you
were
chased about
for
uncounted hours
by
conscientious
teachers.
By reason
of
your past experience, you
would
cer-
tainly regard everyone
with disdain who should
pronounce
even
the
most
out-of-the-way proposition
of
this
science
to
be
untrue.
But
perhaps
this
feeling
of
proud
certainty
would
leave
you
immediately
if
some one were
to
ask
you:
"What, then,
do
you
mean
by
the assertion
that
these
propositions are
true?"
Let
us
proceed to give
this
question
a
little consideration.
Geometry sets out
from
certain
conceptions
such
as
"plane,"
"point,"
and
"straight
line," with which
we are
able
to
asso-
ciate
more
or
less definite
ideas,
and
from
certain
simple prop-
ositions
(axioms) which,
in virtue of these
ideas,
we are
inclined
to
accept as
"true."
Then,
on
the
basis
of
a
logical pro-
cess,
the
justification
of
which
we
feel ourselves
compelled to
admit, all
remaining propositions
are
shown
to
follow
from