Final answer:
Charles Lyell's concept of uniformitarianism proposed that geological changes occur gradually due to constant natural processes, which profoundly impacted scientific thought by influencing the development of Darwin's theory of evolution and contributing to the Enlightenment's empirical approach to inquiry.
Step-by-step explanation:
The concept proposed by Charles Lyell that had a profound effect on 19th-century scientific thought was the idea of uniformitarianism. This was the notion that the same natural laws and processes that operate in the universe now, have always operated in the universe in the past and apply everywhere in the universe. Uniformitarianism emphasized that geological change occurred gradually over long periods and contradicted the idea that cataclysmic events shaped Earth's surface. Lyell's work, particularly his influential book Principles of Geology, helped to establish the vast age of the Earth and had a significant impact on contemporary scientists, including Charles Darwin, whose theory of natural selection was influenced by Lyell's ideas about gradual change and the Earth's age.
Lyell's views on geological change and the age of the Earth also had broader implications, contributing to the shift towards a more methodical and empirical approach to scientific inquiry, laying groundwork for modern geology and evolutionary biology, and were part of the intellectual climate that characterized the Enlightenment and the Scientific Revolution.