[...] What is the relationship between art and knowledge? Should art be conceived as a form of knowledge? Here the concept of visual ideology can be of use. What is the relationship between art and visual ideology? Let us begin by replacing the word 'art' by 'production of pictures'. This empirical term refers back to the simple and concrete fact of the production of certain two- or three-dimensional objects on which lines and colours have been variously placed, and it is preferable to the ambiguous and emotive term 'art'. It is not a precise term, and is retained purely as an indication of the type of production under discussion. On the other hand, visual ideology is to be understood as comprising the essential aspect of the objects which belong to the domain of the production of pictures. Every picture, whether considered as a major or minor work of art, belongs to a collective visual ideology while at the same time possessing its own unique features. This is common to all pictures, and is what makes each one different. Thus visual ideologies form the essence of the production of pictures. If this is so, the question as to the relationship between the latter and knowledge should be replaced by the following paradoxical question: what is the relationship between visual ideology and knowledge? At first glance even the existence of such a relationship may seem dubious. In fact, strictly speaking one cannot but assert that such a relationship does not exist. Visual ideology, with its double aspect of comprehension—misapprehension and illusion—allusion to reality, bears no relation to the scientific knowledge of this reality. Visual ideology and scientific knowledge are two distinct realities which do not coincide. [...]
In fact, if it is true that the essence of every picture lies in its visual ideology, it is also true that in the course of history one can discern two different kinds of visual ideology manifesting themselves in individual paintings: one which I shall subsequently call 'positive visual ideology' and one which I shall call 'critical visual ideology'. Positive visual ideology implies that there is no apparent contradiction in the relationship between a work's visual ideology and other types of ideology to which some elements of the picture refer. This positive, non-antagonistic relationship can go so far as to glorify other types of ideology through visual ideologies (this is the case with political and religious allegories, for instance).
On the other hand, critical visual ideology implies that a work's visual ideology exerts a critical function in regard to other non-visual kinds of ideologies, some elements of which are to be found in the work. Criticism is carried out through the treatment of the work's subject.
So, from the point of view of the relationship between art and knowledge, both positive and critical ideology (in their problematical relationship with other types of ideology) reveal and help us to 'know' their relationship with the overall ideology of a social class, and eventually their relationship with some contemporary non-visual ideologies. However, this kind of knowledge is not scientific but rather is felt or experienced, and requires the art historian's intervention in order to be transformed into scientific knowledge.