unattainable

Logically, they know the goal itself is unattainable, but the endeavour to get there can take them to new heights.

"With our new system, we can achieve levels of efficiency that were previously almost unattainable," says Prof. Harald Giessen, Head of the 4th Physics Institute at the University of Stuttgart.

A Jewish homeland in backwaters of the Ottoman empire seemed unattainable, and pressing domestic concerns like slavery and temperance took precedence.

Critics say they are often doubly flawed: overly expensive if targets prove easier than predicted; and counterproductive if the targets become unattainable and executives see little reason to stick around.

"But for it to become truly sustainable, there would need to be a profound change in production," she told AFP, adding that the industry continued to sell "an unattainable ideal".