In Middle English the old inflected infinitive lost its supine function and gradually replaced the uninflected infinitive in all positions, except in the complementation of moal and a limited number of other verbs. According to most linguists, the choice between the to infinitive and the bare infinitive was either lexically or structurally conditioned. The theory of linguistic change as the assertion of weaker or stronger linguistic variants postulates the affinity of stronger variants for more complex, i. e. functionally marked grammaticall environment. The author tests the validity of the theory against the assertion of the English to infinitive at the expanse of the bare infinitive after the Norman Conquest. The results confirm the initial hypothesist that the degree of formal marked­ ness of the infinitive concurred with the degree of the functional markedness of grammatical pa­ rameters.