The cognition of material things could not be denied to the pure understanding; but as this was not an innate cognition and could not be acquired by it, they were under the necessity of establishing some communication by means of which the understanding might comprehend objects without soiling its purity by sensible species. The imagination contained them, already purified from the grossness of the external senses; in it they existed more aerial, purer, and less remote from immateriality; but they were still at an immense distance from the intellectual order, and had themselves to support the burden of those material conditions which never allowed them to attain the altitude necessary to be put in communication with the pure understanding. In order to know, the understanding requires forms to unite themselves to it intimately; and although it be true that it discerned them far down in the lower regions of the sensitive faculties, yet it could descend to them without compromising its dignity, and denying its own nature. In this conflict they required a mediator; it was the acting intellect. We will now proceed to explain the attributes of this faculty. 49. The sensible species contained in the imagination, the true picture of the external world, were not of themselves intelligible, because enveloped, not with matter properly so called, but with material forms, to which the intellectual act could only indirectly refer. If they could have discovered a faculty capable of rendering intelligible what is not intelligible, this difficult problem would have been satisfactorily solved; as in this case the mysterious transformer by applying its activity to the sensible species, would elevate them from the category of imaginary species, _phantasmata_, to that of pure ideas or sensible species, and thus make them serve the intellectual act. This faculty is the acting intellect; a real magician which possesses the wonderful secret of stripping sensible species of their material conditions, of smoothing every roughness which prevents them from coming in contact with the pure understanding, and transforms the gross food of the sensitive faculties into the purest ambrosia, fit to be served at the repast of spirits. 50. This invention merits to be called ingenious rather than extravagant, poetical rather than ridiculous. But its most remarkable feature is, that it involves a profound philosophical sense, as well because it marks an ideological fact of the highest importance, as because it indicates the true way of explaining the phenomena of intelligence in their relations to the sensible world. This remarkable fact is the difference, even with respect to material objects, between sensible representations and pure ideas. The indication of the true way consists in presenting the intellectual activity as operating upon sensible species, and converting them into food for the mind.