Passage Summary: If science convinces everyone that we aren't actually in control of our own behavior, we will stop feeling guilty when we do bad things, which will eventually destroy society's moral fabric.

Conclusion: Believing that humans are merely natural objects controlled by external forces will inevitably cause a decline in general morality.

Reasoning: A lack of belief in personal responsibility prevents people from feeling shame for immoral acts, and a lack of shame leads to a breakdown in societal morals.

Analysis: The historian provides a logical chain: No Responsibility → No Shame → Moral Decline. However, the conclusion introduces a new concept: 'theories that regard humans as natural objects subject to forces outside their control.' To make this argument airtight, we must bridge the gap between being a 'natural object' and having 'no responsibility.' We are looking for an assumption that explicitly links these two ideas. If we assume that being subject to external forces means one is not responsible for their actions, the conclusion follows perfectly.