Learn Polish: Człowiek nigdy nie wie, jaka zasada obowiązuje.

In Polish, człowiek (literally "a human" or "a person") is frequently used with a third-person singular verb like wie to talk about universal experiences or general truths. It perfectly captures the English generic "you" or "one" (e.g., "you never know" or "one never knows").

Could I just say nigdy nie wiesz instead of using człowiek?

Yes, using the second-person singular nigdy nie wiesz is also a very common and natural way to express the generic "you" in Polish. However, using człowiek adds a slightly more philosophical or universally shared tone to the statement.

What does obowiązuje mean here, and what is its dictionary form?

The infinitive is obowiązywać, which means "to be in force," "to be valid," or "to apply" (usually referring to rules, laws, or tickets). In this sentence, jaka zasada obowiązuje simply means "what rule applies" or "what rule is currently in effect."

Why is there a comma before jaka?

Polish grammar strictly requires a comma between clauses that have their own verbs. Because Człowiek nigdy nie wie and jaka zasada obowiązuje both contain conjugated verbs (wie and obowiązuje), they must be separated by a comma.