The agent internally represents its world/environment in its knowledge base.Sentences are representations in some language.Facts are claims about the world that are true/false.Sentences represent facts in the world.Meaning connects sentences to their facts.A sentence is true if what it represents isactually the case in the current state of world.Proper reasoning ensures that conclusionsinferred from the KB are consistent with reality.That means they represent new facts that actually follow from the original facts (represented by sentences in the KB).