Double Loop thinking is the idea that we have to take a double loop with all the decisions we make. The world is dominated by 'single loop thinking' ie what has happened before will obviously happen again. So if you are expert, one solution is all you need for no matter how many problems you come across. This is how we risk 'skilled incompetence' because we ignore change and eventually the consequences of a 'single solution' build up into a severe backlash - such as the financial crisis we have at the moment. For too long we have solved our financial problems with one simple answer - ignoring any danger signals and ignoring sources of fundamental change. So much change that single loop thinking becomes extremely dangerous.
Double Loop thinking means that we not only adjust actions to consequences but we also question and adjust the mental model that produced those actions in the first place because change is constant and one solution that worked in the past may produce a result in the short term but may have long term negative consequences because we have not examined the fundamental unconscious mental model - the reason the problem occurred in the first place.
This is why we have so many problems in society, we think we can use solutions that worked 10 years ago today when too much change has occurred and it does not work. We need more thought about what is happening and why. Sadly deep thinking about problems does not seem to be important.
Single Loop thinking is 'lazy' thinking, it was first proposed by Argyris and Schon (1978).
I have written about this before - see the following post - Easter 1940