Abolitionists had meantime evolved a precisely contradictory
theory. They asserted that the Constitution gave no warrant for
property in man, except as held under state laws; that with this
exception freedom was guaranteed to all; that Congress had no
more right to make a slave than it had to make a king; and that
it was the duty of Congress to maintain freedom in all the
Territories. Extremists expressed the view that all past acts
whereby slavery had been extended were unconstitutional and
therefore void. Between these extreme conflicting views was every
imaginable grade of opinion. The prevailing view of opponents of
slavery, however, was in harmony with their past conduct and
maintained that Congress had complete control over slavery in the
Territories.

When the Mexican territory was acquired, Stephen A. Douglas, as
the experienced chairman of the Committee on Territories in the
Senate, was already developing a theory respecting slavery in the
Territories which was destined to play a leading part in the
later crusade against slavery. Douglas was the most thoroughgoing
of expansionists and would acknowledge no northern boundary on
this side of the North Pole, no southern boundary nearer than
Panama. He regarded the United States, with its great principle
of local autonomy, as fitted to become eventually the United
States of the whole world, while he held it to be an immediate
duty to make it the United States of North America. As the son-
in-law of a Southern planter in North Carolina, and as the father
of sons who inherited slave property, Douglas, although born in
Vermont, knew the South as did no other Northern statesman. He
knew also the institution of slavery at first hand. As a