In general terms, naturalism is a philosophy that recognizes no other reality aside from nature and the world perceived by the five senses. Naturalism, one of the most significant products of the 19th century atheistic atmosphere, influenced Darwin and drove him to offer an atheistic explanation for life. According to this way of thinking, nature itself was regarded as its own creator and arbiter. Concepts such as Mother Nature or clichés such as "Nature gave some people superior abilities; nature made humans what they are," are still widely employed today, but are the result of preconceptions imposed by naturalism.
Naturalists were great admirers of the perfection in the physical world, yet found it difficult to give a satisfactory answer to how this came into being. Since they adopted positivist dogma, and believed only in concepts whose existence could be established by means of experiment and observation, they fiercely rejected the fact that nature was created by Allah. In their view, nature created itself.
Darwin's theory served naturalist/materialist philosophy, or to be more accurate, the atheism that underlay it. It therefore received support and was imposed on society as if it were a major scientific truth. Otherwise, it would have been regarded as the speculation of an amateur biologist and quickly forgotten.