Final answer:
The Civil War was caused by the South's desire to strengthen and expand slavery, according to Lincoln.
Step-by-step explanation:
Lincoln argues that the Civil War was caused by the South's desire to strengthen and expand slavery. This was a major point of contention between the North and the South, with the North advocating for the abolition of slavery and the South fiercely defending it as an essential part of their economy and way of life. The issue of slavery ultimately led to the secession of Southern states and the outbreak of the Civil War.
Learn more about Causes of the Civil War