So far, we haven't heard any evidence that doesn't amount to "trust us", and that's a bit of a problem.
Especially when we find out that our allies aren't quite as convinced as we are. The lede is pretty straightforward:
Syrian government forces may have carried out a chemical weapons attack close to Damascus without the personal permission of President Bashar al-Assad, Germany's Bild am Sonntag paper reported on Sunday, citing German intelligence.
Kind of destroys any rationale for attacking, doesn't it?