 According to Paul, the qualities which are the adequate and per se object of the exterior senses cause a peculiar modification in the bodily organs, that is the presence in them of a forma intentionalis or species sensibilis, which does not imply any material mutation in the organ itself, as such a form is a resembling image (similitudo) of the real form which started the process totally lacking extension, and therefore unable to modify in any way the matter of the bodily organs (cf. SN, p. v, ch. 23, fol. 79va, and ch. 30, fol. 84rb). As a consequence, Paul affirms that the species sensibilis is a pure form without matter in a two-fold sense: it is not grounded on matter, and it has no extension. Yet, as a resembling image of a real form it contains in itself a sort of logical description of the matter to which the real form gives structure (see SN, p. v, ch. 23, fol. 79 vb). When the species meets the potentia sensitiva of the bodily organ, a sensation is produced, by means of which the soul becomes aware of the external existence of a certain reality (SN, p. v, ch. 28, fol. 83ra). This process is totally passive, as exterior senses can give birth to sensations only in virtue of the actual presence of the material object (SN, p. v, ch. 10, fol. 71va-b). The species sensibilis present in one of the exterior senses and the species sensibilis present in the sensus communis (and in the other internal senses), differ specifically (specifice) from each other, since they are images of objects of different types. In fact, the species present in the general sense is a species of species, as it is not the logical image of the external quality which caused the process of sensation, but an image of the species present in the exterior sense (SN, p. v, ch. 28, fol. 83ra). The higher level of sense-knowledge is therefore qualitatively distinct from the lower. At the higher level, every passage from a faculty to another entails a sort of purification of the forma intentionalis, which progressively loses the information on the individual characteristics of the external object (SN, p. v, ch. 40, fol. 90va). So the perceived thing is first apprehended by the cogitativa as this singular bearer of certain properties, then as a bearer of certain properties, a change that Paul qualifies as a transition from the condition of intentio singularis signata to the condition of intentio singularis vaga (In De an., III, t.c. 11, fol. 137rb). Not only does the cogitativa effect the transformation of the intentio singularis signata into an intentio singularis vaga, it also abstracts the substance, which is a sensibile per accidens (something accidentally perceptible) from the perceived accidental properties which are sensibilia per se (perceptible by themselves—In De an., III, t.c. 11, fol. 137rb; see also SN, p. v, ch. 11, fol. 72ra).