Art historians have long debated whether a newly discovered painting is an authentic work by Caravaggio or a contemporary forgery. Chemical analysis of the pigments shows they are consistent with materials available in the early 17th century when Caravaggio worked. The painting technique, including the dramatic use of light and shadow, matches Caravaggio's distinctive style. X-ray examination reveals no underdrawing, which is consistent with Caravaggio's known practice of painting directly onto canvas. However, there is no documentary evidence of the painting's existence before it appeared at auction in 1960. Despite this gap in provenance, experts have concluded the painting is an authentic Caravaggio based on the technical and stylistic evidence. Which one of the following is an underlying assumption of the above argument?