To  affirm  that  every  distinct  species  of  things,  is  endued  with  specific  oc-
cult qualities,  by  means  whereof  the  things  have  certain  active  powers,
this,  indeed,  is  doing  nothing.  But  ito  deduce  from  the  phenomena  of  na-
ture, two  or  three  general  principles  of  motion,  and  then  to  explain  how  the
properties  and  actions  of  all  copbreal  things  follow  from  these  principles;
thi^  would  be  a  great  progress  in  philosophy,  though  the  causes  of  those
principles  were  not  yet  discovered.  Again — I  have  explained  the  pheno-
mena of  the  Heavens  and  the  sea  by  the  force  of  gravity;  but  the  cause  of
gravity  I  have  not  yet  assigned.  It  is  a  force  arising  from  some  cause
which  reaches  to  the  very  centre  of  the  sun  and  planets,  without  any  dimi-
nution of  its  force,  and  it  acts  not  proportionally  to  the  surfaces  of  the  par-
ticles it  acts  upon,  as  mechanical  causes  use  to  do,  but  proportionally  to
the  quantity  of  solid  matter.  And  its  action  reaches  every  way  to  immense
distances,  decreasing  always  in  a  duplicate  ratio  of  the  distances.  But  the
cause  of  these  properties  of  gravity,  1  have  not  yet  found  deducible  from  the
phenomena,  and  hypotheses  I  frame  not.
30  Opinions  of  Philosophers,  &?c.
