Everyone seems to agree that sustainable development is a good thing.

But views differ over what it actually is – and consequently, how we should achieve it.

SEE ALSO Overview The overcrowded ark TALKING POINT Sustainable development - are we doing enough?

And the list of difficult questions shaping opinions is long:

How bad is the current state of the planet?

Is there a conflict between protecting the Earth and helping the poor?

How much faith should we have in new technologies?

What sort of lifestyles can the planet sustain for everyone – and what sort of lives should we and our children want anyway?

How big a gap between rich and poor is acceptable – and what is the best way of alleviating it?

Do free market policies help or hurt the poor and the environment?

Click on the bar to see how five different thinkers respond to these questions.