eventually be either completely free or completely slave holding.
Explanation:
Abraham Lincoln believed that those two views are derived on basic humans principles in regard of how we should see other human being that different from us.
Those who believe all people are equal regardless of their skin will oppose slavery since they found the idea of treating other humans like animals are abhorring. Those who believe a certain race is superior than the other will always support slavery.
These two different view of humanity will not be able to co-exist with one another under one nation. This is why Lincoln say that statement : Eventually be either completely free or completely slave holding
