In the philosophy of naturalism, the uniformitarianism assumption is 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. It has included the gradualistic concept that "the present is the key to the past" and is functioning at the same rates. Uniformitarianism has been a key principle of geology, but naturalism's modern geologists, while accepting that geology has occurred across deep time, no longer hold to a strict gradualism.
Uniformitarianism was formulated by Scottish naturalists in the late 18th century:
James Hutton – a geologist, started Uniformitariansim
John Playfair – refined James Hutton’s work
Charles Lyell – a British Lawyer and foremost Geologist, popularised Uniformitarianism through his book entitled “Principles of Geology” in 1830. He was also a close and influential friend to Charles Darwin.
William Whewell – coined the word “Uniformitarianism”.
HISTORY
The earlier conceptions likely had little influence on 18th century European geological explanations for the formation of the Earth. Abraham Gottlob Werner proposed Neptunism where strata were deposits from shrinking seas precipitated onto primordial rocks such as granite. In 1785 James Hutton proposed an opposing, self-maintaining infinite cycle based on natural history and not on the Biblical record.
The solid parts of the present land appear in general, to have been composed of the productions of the sea, and of other materials similar to those now found upon the shores. Hence we find reason to conclude:
1st -That the land on which we rest is not simple and original, but that it is a composition, and had been formed by the operation of second causes.
2nd -That before the present land was made, there had subsisted a world composed of sea and land, in which were tides and currents, with such operations at the bottom of the sea as now take place. And,