Complex sentence: Dolben's speech was disputed by Lord Penrhyn, one of the two MPs for Liverpool, who claimed that captains were motivated to preserve the lives of as many slaves as possible, so that they could profit from their sale.
Split into simpler sentences: Dolben's speech was disputed by Lord Penrhyn, one of the two MPs for Liverpool. He claimed that captains were motivated to preserve the lives of as many slaves as possible, so that they could profit from their sale.