The service learning method ties in well with a teaching philosophy known as constructivism. Constructivism is an educational theory rooted in psychology and sociology. It asserts that learners construct knowledge from previous knowledge rather than passively absorbing knowledge from outside sources. Furthermore, learning includes both creation of new factual knowledge and understanding the connections between different nodes of knowledge. Service learning provides an environment where students can actively construct knowledge while engaging in actual projects. The reflection portion of service learning gives students time to create connections between old and new knowledge.
While accepted by many, some educators have criticized constructivism both epistemologically and pedagogically. Pedagogically, critics claim that a constructivist approach gives students in-depth knowledge but not breadth of knowledge. Since in a constructivist approach takes a significant amount of time to allow students to create new knowledge and relate it to previous knowledge through reflection, instructors usually cannot cover a large amount of material. However, while this may become a real concern for many courses, the specific role of service learning plays in engineering school courses mitigates these concerns. Service learning typically appears in introductory or optional courses in the engineering school. The goals of these courses is not to much to gain a detailed and broad understand of a field, but rather to have a real world engineering experience. This is notably different from courses where students must obtain vast amounts of accurate knowledge for precise calculations.
Critics also worry that a constructivist approach to education leaves the learner too disconnected from reality since it constantly focuses on building new knowledge based off of pre-existing knowledge. Thus, theoretically, as they continue building knowledge off of their pre-existing knowledge in isolation, their view of the world could slowly become skewed from reality. While this may be a weakness for many courses, in service learning, students work to create real solutions for a real customer. Thus their ideas must be resolved, not only with fellow engineering team members, but also with reality.