Passage Summary: The author argues that we shouldn't just look at the tiny impact of one person's choice, like skipping a vote or stealing something small. Instead, we have to judge an action by what would happen if everyone did it; if the mass result is bad, the individual act is wrong.

Conclusion: An individual's action or failure to act is morally wrong if the widespread adoption of that behavior would result in social harm.

Reasoning: The author uses the example of voting and theft to illustrate that while a single instance might have a negligible impact, the cumulative effect of many people doing it would destroy social institutions or society itself.

Analysis: This argument moves from a specific case (voting) to a general moral principle. The 'main conclusion' is the broad rule the author is trying to establish: the morality of an act depends on the consequences of its collective performance. I identified this by seeing how the voting example and the theft analogy both serve to support this 'universalizing' moral standard. Look for the statement that expresses this general rule rather than just the specific examples. It's a classic philosophical 'what if everyone did that?' argument.