Abiogenesis

And thus the hypothesis that living matter always arises by the agency of pre-existing living matter, took definite shape; […] It will be necessary for me to refer to this hypothesis so frequently, that, to save circumlocution, I shall call it the hypothesis of Biogenesis; and I shall term the contrary doctrine—that living matter may be produced by not living matter—the hypothesis of Abiogenesis.

The assertion of [Louis] Pasteur is justified, that the onus probandi [burden of proof] lies with abiogenesists, since there is no experience of any living form more than ¹⁄₁₀₀₀ of an inch in diameter springing to life out of inorganic matter; it is therefore vastly improbable (needing most cogent evidence to prove), that any form less than ¹⁄₁₀₀₀ of an inch in size can be made to spring into life from inorganic matter. While abiogenesis is unproved, we hold to the conclusion that vital force is not the mere outcome or resultant of any or all of the other cosmic forces.

Life began. There was one abiogenesis when something happened to turn inanimate matter into animate cells. And it happened only once. There are no abiogeneses today. Human life is continuous. Human persons are discontinuous and individual.

According to [Carl] Nägeli, the highest forms have evolved from the oldest cells produced through abiogenesis, and the lower forms are, depending on their position in the hierarchy, the descendants of respectively more recent abiogenesis.

Although abiogenesis, the spontaneous creation of a living system under appropriate conditions, must have occurred at the end of the prebiotic world, spontaneous generation of life no longer occurs.