In this work Hutton proposed that the causes acting on the world today also acted in the past. This means that the rocks of the Earth were formed by processes which we can see operating today. These processes, though very slow (gradualism), made the world what it is today. The idea is part of a wider philosophy called the philosophy of naturalism.
Hutton's ideas were popularised by John Playfair in 1802 in Illustrations of the Huttonian theory of the Earth, and by Charles Lyell in his Principles of geology (1830 to 1833). The phrase "the present is the key to the past" is Lyell's most famous quotation.
Uniformitarianism in geology is opposed by catastrophism, the idea that major changes in the Earth take place through sudden and violent events.
- Whewell W. 1847. Philosophy of the inductive sciences, new edition, part 1, Book X, Chapter III 'Of the doctrine of catastrophes and the doctrine of uniformity'. John W. Parker, London. p665
- Whewell W. 1857. History of the inductive sciences. 3rd ed, Parker, London. vol 3, p508