The document discusses four approaches to knowledge: common sense, certainty, radical doubt, and relativism. It also examines three tests of truth: correspondence, coherence, and pragmatic. Common sense holds that knowledge is organized based on a coherent picture of the world, but this view has limitations as common sense can be vague, untested, and based on hearsay. Certainty considers knowledge as what is known with absolute certainty, but our ways of knowing have limits and introduce degrees of certainty. Radical doubt argues we can never be 100% certain, while relativism claims there is no absolute truth independent of beliefs as all views are equally valid, though this poses issues like how to determine what is wrong. Correspondence