Numerous explanations have been put forth for the uses and derivations of tenses. This paper attempts to show that none of these explanations is satisfactory, since they cannot account for many ways in which tenses are used in English and other languages. While this paper does not try to present an adequate theory, it gives evidence that such a theory, at the very least, must be able to incorporate in its underlying structures concepts such as the interrelationship of the actual time of occurrence of events with the involvement of the speaker, hearer, or other participants in these events.