J. J. Winckelmann's approach treats art as a universal; he regards Greek imagery as art in a relatively uncomplicated fashion. Winckelmann instigated the study of art history with an analysis of Greek figures, while the roots of the philosophy of art lie in Alexander Gottlieb Baumgarten's description of aesthetics, whose origins he sought in ancient Greek etymology and language. Instead artworks could only be distinguished by their context, by their symbolic signification and their interpretation as objects displayed in art galleries; they are components of the 'artworld'. In P. Tacon and C. Chippindale's discussion of 'inside' vs. 'external' knowledge in rock art studies, one sees the distinction between anthropology and archaeology articulated afresh. Informed approaches 'depend on some source of insight passed on directly or indirectly from those who made and used the rock art – through ethnography, through ethnohistory or through modern understanding known with good cause to perpetuate ancient knowledge'.