Our knowledge of nature is just that: 'our knowledge.' The activity we call 'science' is created and pursued by humans in historical time. It certainly reflects the natural world, and is limited by what there is for us to see (or detect where we cannot see). But science also reflects human preoccupations, and is shaped powerfully by what we want to see and to know. This leads us to an interesting question: what and how much of science is 'out there' and what and how much is 'made up'? That is the subject of this course: looking at the 'out there' and the 'made up' in physics, biology, geology, natural history, and in that branch of mathematical investigation called 'complexity theory.'