We acquire knowledge not only through reading books but through our senses. When we touch ice for the first time, we realize through our sense of touch that it is cold. Same can said about hearing a gun shot. We know that a shot from a gun when we hear it through our ears. The sensations that we get not only help identify certain things but helps assess if these things will be harmful or beneficial. When we are able to identify what is harmful, then we learn to avoid it. If it is good then we can use it.