Economist: Some sociologists argue that because capitalism intrinsically involves competition, it weakens the ties between the people of a community.
Conclusion
Modern capitalism promotes communal ties.
Evidence
Modern capitalism requires that there by large corporations.
Evaluate
The first sentence isn't part of the argument (it's ascribed to some sociologists). Our author ends up disagreeing with this position. The "Although ..." part of the 2nd sentence is a concession to this opponent, so only the second half of the 2nd sentence is her premise.
Thus, we have very little to look at or think about here. The author makes a move from, Because capitalism requires corporations, we know capitalism promotes communal ties.
Goal
Look for an answer addressing the assumption that "corporations promote communal ties".