Step 1: Paracelsus is called the Father of Toxicology. He gave the foundational principle that the dose makes the poison, that any substance can be toxic at a sufficient dose.
Step 2: Mathieu Orfila is regarded as the Father of Modern Toxicology, as he established toxicology as a distinct scientific and forensic discipline, so he is not the answer to this classic stem.
Step 3: Galen was an ancient Greek physician associated with early medicine and anatomy, and Francis Galton is linked with fingerprints and biometrics, so neither relates to founding toxicology.
Step 4: Therefore Paracelsus is the correct choice.