This is true of human life, water, heat and power. Anyone who has certain attributes that can be perceived can predict the decline of these attributes according to a lot of experience. Therefore, any existence with certain attributes and composed of these attributes can never be the root or original principle of things. Anaximander reasoned that a real existence can't have any definite attributes, otherwise it will be born and doomed like everything else. In order to keep the generation from stopping, primitive people must be uncertain. The immortality and eternity of primitive people is not an infinite and inexhaustible thing as anaximander's interpreters usually think, but it does not have some quality that will lead to its decline. Therefore, it was named apeiron. The primitive named in this way is higher than generation, thus ensuring both eternity and unimpeded generation process. Of course, this ultimate unity in an uncertain body and in the mother's womb of everything can only be called by people in a negative way, and it is impossible to find a title for it from the existing generation world. Therefore, it can be considered that it is similar to Kant's thing-in-itself in the eighteenth century.