@ryan from the srd, actually: "Your Spellbook
The
spells
that
you
add
to
your
spellbook
as
you
gain
levels
reflect
the
arcane
research
you
conduct
on
your
own,
as
well
as
intellectual
breakthroughs
you
have
had
about
the
nature
of
the
multiverse.
You
might
find
other
spells
during
your
adventures.
You
could
discover
a
spell
recorded
on
a
scroll
in
an
evil
wizard’s
chest,
for
example,
or
in
a
dusty
tome
in
an
ancient
library.
Copying
a
Spell
into
the
Book.
When
you
find
a
wizard
spell
of
1st
level