Most people who are asked to read these sentences report that they think John is probably a schoolboy. Since this piece of information is not directly stated in the text, it must be an inference. Other inferences for different readers. are that John is walking or that he is on a bus. These inferences are clearly derived from our conventional knowledge, in our culture, about "going to school, and no reader has ever suggested that John is swimming or on a boat, though both are physically possible, if unlikely, interpretations.