Logic in Western philosophy can have formal perfection, but limited epistemic value. "All chairs are 50 feet tall, my mother is a chair, therefore my mother is 50 feet tall" is a sound piece of logical deduction, but it doesn't tell us anything true or useful about the world. In Indian intellectual tradition, logic is more like scientific reasoning - its aim is to increase knowledge. This week we're looking at logic in one of the classical schools of Indian philosophy.