  Ockham's logic marks an important, though not the only important, step in the process that might be described as a progressive ‘mentalization’ of sign. The idea behind this process is the contention that without some sort of ‘intentionality’ the phenomena of sign, signification and semiosis in general must remain inconceivable. This tendency of relocating the notions of sign and signification from the realm of spoken words to the sphere of the mind is characteristic of the mentalist logic arising in the early 14th century, and remaining dominant throughout the later Middle Ages. Words or signs, insofar as they concern rational discourse, were traditionally held to be the essential subject matter of logic. According to mentalist logic, however, the ‘words’ or ‘signs’ primarily relevant to logic are not the spoken words, but the trans-idiomatic mental words (verba mentis) or mental concepts. Thus, in later medieval logic, as already in Burleigh and Ockham, the mental sign will be the focus of logical semantics. According to a distinction introduced by Peter of Ailly (1330–1421) in the second half of 14th century,