 In addition to providing the systematization of the elements used in modern chemistry, Mendeleev also gave an account of the nature of elements which informs contemporary philosophical understanding. He explicitly distinguished between the end of analysis and actual components conceptions of elements and while he thought that both notions have chemical importance, he relied on the actual components thesis when constructing the Periodic Table. He assumed that the elements remained present in compounds and that the weights of compounds is the sum of the weights of their constituent atoms. He was thus able to use atomic weights as the primary ordering property of the Periodic  Table.[3]