This is a translation from French by Stamatios Valvis of Haeckel 's article of the same name. The original article is a response to Virchow, with the intent of defending monism, the idea that is that the soul is inherently grounded in the materialistic workings of the body. The article is extensively annotated by Valvis, which makes it clear that he considers it a rebuttal to Skaltsounis.