While a good case can be made for asking the upper-income elderly to pay higher premiums, varying the benefit according to beneficiaries' incomes is simply impractical.

The sheer numbers, and the complexity of the groups, made it simply impractical for anyone to attack anyone.

Tim Eggar, the Government's second-ranking education official, said the initial tests for 7-year-olds were simply impractical.

It is simply impractical to use batteries in these devices.

The utility decided it was simply impractical to spend the money required to refurbish the 32-year-old facility, whose continued operation has been opposed by environmental activists for years.

Plus, infants and toddlers have a way of making certain outfits simply impractical.

Spraying the roughly 150-million-plus acres of America's last great wilderness preserves is simply impractical.

The intricately constructed girdle bindings were simply impractical after a certain point.

"It's simply impractical to do what I want to do, here, at this time," Charles said.

Some tests are simply impractical, and environmental conditions can be hard to predict over a systems life-cycle.