Passage Summary: The author claims that lawyers using a dictionary is no different than chemists using the periodic table, because both are just handy tools for looking up standard information.

Conclusion: Using ordinary dictionaries to interpret legal terms is as justified as chemists using the periodic table.

Reasoning: Both dictionaries and the periodic table provide a standard, agreed-upon set of background information that helps professionals solve specific problems in their fields.

Analysis: The argument relies on an analogy, so to weaken it, we should look for a fundamental difference between the two things being compared. The periodic table represents objective, unchanging chemical properties, whereas language in a dictionary is often imprecise, evolving, or subject to multiple interpretations. An answer that highlights how legal terminology requires more nuance or context than chemical elements would effectively undermine the comparison.