But in terms of big and challenging ideas, there simply aren't any.

Why is that such a challenging idea?

We must insure that it contains challenging and provocative ideas.

A new consulting practice, based on a challenging and proven idea, opens up but leading edge companies never become clients.

This is a challenging idea for some people.

The first challenging idea is to convert battery voltage readings into power consumption.

Dr. Crew will need to work hard to save his challenging ideas from the same fate.

He continued experimenting with the one big challenging alternating-current idea that was occupying his mind.

His challenging ideas caught the attention of the intellectuals; he lectured all over China and abroad.

Splendid objects are here to be seen but challenging ideas are nowhere to be found.