Complex sentence: Sohn-Rethel pondered the question of what holds society together, when all production is carried on by private agents acting independently of each other, concluding that society can in that case cohere only through "buying and selling".
Split into simpler sentences: Sohn-Rethel pondered the question of what holds society together, when all production is carried on by private agents acting independently of each other. He concludes that society can in that case cohere only through "buying and selling".