Complex sentence: Parfit concedes that his and rival Reductionist theories rarely conflict in everyday life, and are only brought to blows by the introduction of out of this world examples, but defends the usage in that they seem to arrouse genuine and strong feelings in many of us.
Split into simpler sentences: Parfit concedes that his theories conflict with rival Reductionist theories rarely in everyday life, and are only brought to blows by the introduction of extraordinary examples. However, he defends their usage in that they seem to arrouse genuine and strong feelings in many of us.