Food for thought is no substitute for the real thing.

But whenever you need something like that, there's no substitute.

It's when we're starving that we only have food for thought.

[Yet the bars, goos, and ices are no substitute for real food.] Energy bars are manufactured products, ... What you're missing from any kind of manufactured product are the benefits from nature -- the chemicals that aren't vitamins or minerals, but are phytochemicals -- which are still beneficial to our health.

A public-opinion poll is no substitute for thought.

Furious activity is no substitute for analytical thought.