@ACuriousMind as I understand it, you get credits for classes. Majors, i.e., certifications that you know something about a subject, require that you have a certain number of credits from classes in that field. You can therefore get multiple majors by getting the required number of credits for each type. This is easier than you'd think, as many classes required for majors overlap - for example, a physics major may require some math classes, and so lead (after more math classes) to a math major.