Passage Summary: If knowing a word's dictionary definition were required for understanding, you'd also have to understand all the words used in that definition; however, babies clearly use words without knowing their dictionary definitions.

Reasoning: No reasoning (Fact Set).

Analysis: This stimulus sets up a conditional chain: Understanding -> Knowing Definition -> Understanding words in the definition. It then provides a counter-example: babies. If we assume babies actually 'understand' the words they use, then the first link in the chain must be false. The logic suggests that dictionary knowledge is not a strictly necessary component of linguistic understanding. Look for an inference that reflects this disconnect between formal definitions and actual word usage.