Pouchet was 60 years old while Louis Pasteur was 37 years old when the heart of the debate about spontaneous generation began. Their opinions on generation originated from two competing theories. Pouchet believed in heterogenesis, which assumed that new living organisms came from inanimate objects, such as air. The parents of these new organisms were not the same species as the new organism. Pasteur supported the germ theory that said microorganisms arose from germs and those microorganisms came from parents of the same species. He supported the idea that germs were mostly everywhere, including things like air and those germs explained the appearance of microorganisms on different inanimate things.