Wolfgang Pauli is known as one of the most famous physicists of the 20th century. Next to an intensive treatment of physics, his impressive correspondence with fellow physicists also demonstrates a vivid interest in psychology and biology. Reflections on the mind-brain problem and on topics such as causality and evolutionary theory are readily present. In this paper, some central passages in this correspondence are discussed and linked to more current debates in philosophy of science and philosophy of biology. It is shown how Pauli speculatively explored how evolutionary theory can find inspiration in quantum theory and in its related concept of observer-dependency. Contra Kalervo Laurikainen's interpretation, it is argued that Pauli's criticism remains true to a naturalistic view on science and biology.