All science, reason and judgement is founded upon assumptions we make about the world. Our scientific theories are only as good as the assumptions upon which they are built. Thomas Kuhn described how these collective assumptions form a paradigm – a way of seeing the world that holds sway over the group mind at any one time. A classic example was the assumption that the heavens revolved around the Earth. Astronomy challenged this assumption, but the religious, political and scientific elite were highly resistant to changing their assumptions. We cling to the assumptions and models of the past because we are comfortable with them and because they serve the interests of powerful people. Only when the evidence for a better paradigm becomes overwhelming do we make the change. We must catalyse this process by keeping our minds open, creative and continually challenge our assumptions.