It is supported by appropriate testimony. It is backed by an appropriate appeal to authority. It is not known to be unacceptable and can serve provisionally as the basis for an argument. Everyone who is a parent is legally responsible for the wellbeing of at least one child. If all dogs have four legs, then Sally's dog must have four legs.
All zebras have stripes.
The earth revolves around the sun. The early bird gets the worm. Smoking causes cancer. All humans must consume liquids to live. Every effect has a cause.