Attendance at my classes is important. By holding a strict attendance policy and keeping to it throughout the course of the semester, I am trying to do several things:
1) Forcing my students to be present and (hopefully) attentive
2) Forcing my students to understand that earning an education is an active process that they have to take part in--my classes are not independent studies
3) Having enough students present to have meaningful, ranging, representative discussions over the readings I give them.

Because my students are community college students largely out of high school, my second goal above seems to be the hardest to make them understand and appreciate. Yet, by the end of the semester the students that do take becoming educated seriously typically excel.