– One has sassata ditthi if one believes that there is a permanent soul (as in Christianity).
– One with uccheda ditthi believes that there is nothing after the death, not even rebirth. Many scientists believe thoughts arise in the brain (material body) and therefore when the body dies, that is the end of the story.
All of them believe that it is the same “person” that goes through various stages as a child, adult, old person, etc.
But in the absolute sense (per Buddha Dhamma) “a person” is a sankata that arose due to past causes and will last until that kammic energy wears out. During its existence it will be subjected to unexpected changes too.
– When that “person” does good or bad kamma, he/she would make causes for more future births (in good and bad existences).
– Thus, that “person” can be reborn a Deva or an animal, for example. There is no “essence” in a “person.” It is all a series of causes and their effects.