Final answer:
Catastrophism is the principle that suggests events in the past happened suddenly and were caused by mechanisms different from those operating today, contrasting with uniformitarianism, which influenced Charles Darwin's ideas on evolution.
Step-by-step explanation:
The principle that states that events in the past occurred suddenly and were caused by mechanisms that are not necessarily operating today is known as catastrophism. Catastrophism is the view that Earth's geological features were primarily shaped by sudden, short-lived, violent events, such as floods or volcanic eruptions. This contrasts with uniformitarianism, which posits that the same natural laws and processes that operate in the present day have always operated in the universe in the past and apply everywhere. While catastrophism was a prevalent belief, influential figures such as James Hutton and Charles Lyell championed uniformitarianism, ultimately shaping Charles Darwin's thinking, as gradual processes provided an analogy for gradual change in biological evolution – a concept known as gradualism.