Definitions:
Def 1: A contingent being is a being such that if it exists, could have not-existed or could cease to exist.
Def 2: A necessary being (or non-contingent being) is a being such that if it exists, cannot not-exist (and therefore could not not-have-existed and cannot cease to exist).
Note: I use ground-reason essentially to do the work of the German Grund, a word which neither the English “ground” nor “reason” sufficiently captures in meaning, since it unites the sides of being and knowing, the ontological and the epistemological, in one.
The Argument
1. A contingent being C exists.
Sy Garte discusses how raised as a red diaper baby, he over came his childhood indoctrination to embrace Christianity. His study of science in graduate school made him question the Markist/atheist beliefs his parents raised him with. 
As philosopher Edward Feser has pointed out, some atheists are simply not intellectually serious. They may be very ignorant or uneducated, directly dishonest, deeply confused, ill-informed, willfully obtuse, ideologically dogmatic, or just plain stupid; the end result is the same: it is not possible or fruitful to have a serious, rational discussion about God with such people. Here are some red flags which will alert you that you are dealing with an intellectually dishonest or defective atheist: