Although Darwin was cautious about making his theories public, what event finally prodded him to publish, On the Origin of Species?

Charles Darwin published his most famous theoretical work, On the Origin of Species, when he eventually overcome his dilemma of the effects of his work to the church. It was commonly known that his theories and principles would not be in accordance to what is thought in the church which caused the delay of publication.

Receiving a letter from Wallace describing Wallace's theory of natural selection.