Formal logic has been considered as one of the advanced topics in computing that students do not grasp easily. But the inherent nature of formal logic makes itself a natural choice for forming an overbearing organizing structure, which can be utilized in providing scaffolding during instructional process. This paper discusses the role of formal logic in teaching information science and information systems. We claim that formal logic can be used to realize the modern instruction design principles by ensuring activation of relevant prior knowledge and experiences when learner moves from one topic to another. The paper also describes the successful implementation and evaluation of an on-line teaching tool utilizing predicate logic notation to assist learners in mastering a difficult to learn Unix/Linux system administration command.