He probably knew of the three-age model of prehistory through the works of Lucretius, Vedel Simonsen, Montfaucon and Mahudel, and decided to sort the material in the collection chronologically. Before Thomsen, this might have been done by mechanically sorting the materials according to their materials or the level of craftsmanship they displayed, but as the provenance of many of the materials were known, he could see that crude artifacts were sometimes found with fine ones and metal artifacts with artifacts of stone. Rather than take a simple technological or evolutionary approach, he realized that the task was to determine in which periods the artifacts had been made.