The fact that economists do not always agree, and that there are alternative "schools" of macroeconomic thought, can sometimes seem confusing. It may help to think about, or discuss in a group, how economics compares to other subjects that you or your classmates have studied. What kinds of changes in the fields of physics or biology have occurred in the past hundred years? Are there major debates, disagreements, and unsettled issues in other fields such as psychology, sociology, or political science?