What did Louis Agassiz believe caused extinctions?

Louis Agassiz believed that extinctions were caused by ordinary physical events, such as climatic and geologic changes, as well as the activity of glaciers.1

However, Agassiz maintained that while these environmental factors could lead to extinction, they were not responsible for the creation of new species. Instead, he adhered to the doctrine of catastrophism, which posits that the organic world resulted from repeated, independent interventions by a supreme being. Consequently, he rejected the theory of evolution, viewing each species as a specific "thought of God" rather than the product of hereditary continuity or environmental adaptation.1