By tense we understand the correspondence between the form of the verb and our concept of time, yet in many cases the simple past tense does not express the past time, but the unreality of an event or has the functions of tentativeness and politeness, this is because bodied experience is the source for humans to understand the outside world, it is the cognitive basis of representation of time in space concept, the past tense is the ‘remote’ tense, the indication of unreality and the tentativeness, politeness in the past tense are realized by grammaticalization of the English language.