Mankind has to introduce sustainable development within the 21st century if basic life conditions are not to be put at risk. Above all, this demands eventually taking note of the limitations of non-renewable energy resources and of the limited capacity of local and global ecosystems to deal with disposal and emissions. For the resulting problems, we have to develop solutions. But sustainability is more than the protection of the natural environment. Justice, social stability, and adequate opportunities for education and employment for all people are of similar importance for our future. Both...