For most Arts and Science programs at U of T, you apply for your specialist or two majors at the end of your first year. Many programs are limited enrollment. Your first year grades plus whether or not you have taken the prerequisite courses determine whether or not you are approved for your specialist or majors. The more popular majors are competitive to get into. But, you can potentially major in two completely different fields. Here is a list of the different programs at U of T. https://www.utoronto.ca/academics/programs-directory If you click on the links and scroll down, if you see a yellow box, it will describe the criteria for being accepted into the major or specialist program.