So far, there seem to be two clear lessons from Chicago's experience.

The event was a clear lesson that construction of the fort must not be delayed any further.

There is at least one clear lesson to be learned from watching someone fall off a cliff.

And there are clear moral lessons here, useful for parents everywhere.

"But I think the clear lesson is to just shut up."

We've learned at least one clear lesson from all this.

We all have a clear lesson to learn from the disastrous attacks of 11 September.

We should face up to this and learn from this clear lesson.

Would this add up to a coherent and clear historical lesson?