How does lincoln's belief in the declaration of independence lead him to reject self-interest as the sole principle of political action

This  was   because  slavery  was   not  accepted  or   approved  by all  all races.  Slavery was  only  accepted  by  the  whites  only.Due  to  this  reason  the  idea about all  men  were created  equal   was  raised  and  hence  no  single  individual  from  whatever  race  is  suppose  to  be   exposed to  slavery.