This is a presentation given to a conference "The History and Future of Our Wetlands" sponsored by Ontario Nature on 2 February 2012. The conference was intended to celebrate decades of efforts to protect Ontario wetlands. The talk surveys several decades of scientific progress in understanding causal factors in wetlands, and the usefulness of this science in managing wetlands for conservation. Particular emphasis is placed on the importance of flood cycles in lakes and rivers, and the importance of infertile habitats, in maintaining biological diversity. Two useful models, the CSR model and the pool and filter model, are introduced and briefly described. A two page handout can be downloaded from Keddy's web site (drpaulkeddy.com/News/Keddy%20--%20Six%20general%20messages%20for%20wetlands%20--%202010.pdf).