The fire that destroyed the Municipal Building started before dawn this morning, and the last fire fighters did not leave until late this afternoon.
Conclusion
Thomas must have seen it, whatever he now says to the contrary.
Rephrase: Thomas saw the fire this morning.
Evidence
The fire started before dawn and lasted until late in the afternoon. No one could be near such a fire and not notice it. Thomas admits he went from his apartment to the library this morning. He has to pass the Municipal Building to get there.
Evaluate
The argument concludes that Thomas saw the fire, despite any claims he may make to the contrary. The conclusion is supported by several premises — the duration and intensity of the fire, Thomas' route from his apartment to the library, and the necessity of passing by the Municipal Building. This follows the common pattern of a rebuttal conclusion where the author rejects a possible counterclaim (Thomas saying he didn't see the fire).
Goal
Find the best available meaning match for *Thomas saw the fire this morning.*