In Soul by Soul, what is Walter Johnson's thesis?

Walter Johnson's Soul by Soul is a
well-researched and well-documented history of slaves encumbered within the "peculiar
institution" of slavery in the South in Louisiana. His thesis shows the human face of
slaves and thoroughly discounts the South's rationalizing theories of African slaves as
inferior creatures incapable of fending for themselves and therefore needing looking
after. Johnson chronicles the daily experiences and the extensive effective
communication networks of the people who were sold into slavery as recorded in legal
papers, diaries, letters and bills of sale, and other
documents.

As well as showing the detailed daily operation
of slave trade and slave life, Johnson shows that slaves had interpersonal relationships
with their owners--and even to some extent with the slave traders who would coach the
slaves on how to present themselves--and could at times influence to whom they were sold
or resold, their return to the salve trader under redhibition laws ("picked a lemon"
laws), and sometimes even forestall the break up of their families. In this way Johnson
presents and proves a thesis that debunks the theories of slaves as non-human or
sub-human creatures, and therewith raises American slavery up from being a meaningless
abstraction that is irrelevant today by showing the contrary: slavery defines national
characteristics and has an influence even today.