Validity: The extracted argument faithfully captures the passage's response to Grünbaum's objection, where broadening the notion of "event" (premise 1), noting that space-time commences at the Big Bang (premise 2), and treating the Big Bang as either the commencing event or an initial state (premise 3) together support the conclusion that one may legitimately inquire about why this event/state existed.
Confidence: Clearly presented as a response to Grünbaum