And in time, someone had the radical notion that she didn't need to stop with one child.

In a world brought up on the idea of a "population explosion," this is a radical notion.

The months spent at Paris in 1792 had only intensified his radical notions.

Putting them under the same roof is a radical notion.

Recycling programs, a radical notion 30 years ago, have become commonplace.

"This is certainly a radical notion for most hospitals," he said.

That would be a radical notion in any state.

This is not, on the face of it, a particularly radical notion.

If you think about this closely, though, it's quite a radical notion.

That science and reason might be applied to the stock exchange was still a radical notion in 1905.