Passage Summary: Some people say you should be a vegetarian for health or for ethics. The author suggests that if meat were actually required for health, the ethical argument might not be strong enough on its own.

Conclusion: The claim that an ethical aversion to harming conscious creatures is a sufficient reason to avoid meat would be less certain if meat were necessary for health.

Reasoning: The author introduces a hypothetical scenario where meat consumption is essential for human health to challenge the idea that ethical concerns alone are always enough to justify vegetarianism.

Analysis: This is a 'Role in Argument' question, so we need to look at the structural function of the specific phrase. The phrase is a 'supposition' or a hypothetical premise. It isn't presented as a fact, but rather as a 'what if' scenario used to test the strength of the vegetarians' second reason. By showing that the ethical reason's sufficiency depends on health factors, the author uses this supposition to undermine the claim that the ethical reason is 'individually sufficient.'