There is life after death. Therefore, dualism is true. E.g. Everyone who has ever lived a long time has died. Therefore, everyone eventually dies. Inference to the best explanation.
E.g. People report life after death experiences.
The best explanation of these reports is that people survive death. Therefore, there is life after death. It is simpler, i.e. requires fewer extra assumptions. It fits better with the rest of what we believe. Therefore, we are justified in believing H1.