Little attention has been attracted to the contrast in meaning between bare infinitive and to-infinitive. In traditional grammar, it has been defined that infinitival to is a function word which has no meaning of its own. And many generative grammarians like Chomsky(1957,1981) hold that to is a morpheme that `can hardly be said to have a meaning in any independent sense` or tense inflectional element. In contrast, I have examined infinitival to is a prepositional element through the usage of two infinitives in Old English and Middle English. This paper is an attempt to explore whether meaning differences exist between bare infinitive and to-infinitive by focusing on the meaning of the infinitive particle to as a preposition. On the syntactic and semantic grounds, I put forward two proposals: i) to preceding the infinitive has a discernable meaning that distinguishes the bare infinitive from the to-infinitive construction-it refers to the sequent movement between the infinitive and the matrix verb in a time continuum, ii) to is capable of evoking an event of non-realized or possible future. Futhermore, considering a wide range of full verbs having different semantic properties such as help, make, have, see, etc, it is concluded that the meaning of the bare infinitive can be characterized as `direct actualization` between the two events, whereas the to-infinitive can be analyzed as `indirect actualization`.