Induction and abduction are well known non-deductive inferences. We shall propose that design is also another form of non-deductive inference, and, based on Barwise and Seligman’s mathematical theory of information flow, construct a formal model of non-deductive inferences. We shall show also that these inferences are interpretable each other, and argue mathematical properties of the model. KEY WORDS Model-Based Reasoning, Case-Based Reasoning, Induction, Abduction, Design, Channel Theory