John-man
Evolutionism is a philosophical position but the theory of evolution is science.
Evolution is an empirical fact. The theory of evolution explains this fact.
Empirical = based on, concerned with, or verifiable by observation or experience rather than theory or pure logic.
The scientific method is an orderly method used by scientist to solve problems, in which a recognized problem is subjected to thorough investigation, and the resulting facts and observations are analyzed, formulated in the hypothesis, and subjected to verification by means of experiments and further observation. No theory of origins can be proved scientifically because the essence of the scientific method is observation and experimentation. One does not have to be a scientist to know that the origin of the universe and man cannot be observed or put to experiment since it is not happening in the present.
At the most evolution falls under historical science. Empirical facts no.
The theory of evolution and atheism are completely unrelated.
To a point. There are theist who believe in evolution. But there are no atheist that believe in creation. Evolution is the handmaiden of atheistism.