Complex sentence: This would categorize as implicit atheists adults who have never heard of the concept of deities, adults who have not given the idea any real consideration, and agnostics who assert they do not believe in any deities (even if they claim not to be atheists).
Split into simpler sentences: This would categorize as implicit atheists those adults who have never heard of the concept of deities, and those adults who have not given the idea any real consideration. Also included are agnostics who assert they do not believe in any deities (even if they claim not to be atheists).