Knowledge implies truth: what is known cannot be false. This is a matter of definition. There are other requirements, too. In the usual case, knowledge of something is not attributable to someone as knowledge unless that person has reason for his belief. But even this is not quite enough, since a true belief based on reasons might still be rejected as knowledge if the reasons were not considered adequate. That is, for a true belief to be knowledge, the reasons or grounds for holding it must satisfy certain standards. Some people convey this by saying that knowledge is a title that beliefs must earn, and that they earn it not simply by being true but by being well grounded.