We are all atheists in certain ways and times. One who believes that he or she can live without partaking of Holy Communion and without the sacraments, and the paternal house of the church. Atheism is death. Atheism is a path having darkness at its end because it separates the secondary light from its source, the primary light. When Lucifer fell, it went into darkness.
Darkness signifies death and non-existence.
The Orthodox Icon depicts the devil in black color, small in size. By this depiction, it shows that it lost its light and true life, being separated from the primary light. Atheism or separating oneself from God is not a like changing one's principles. It is a matter of life or death. Let us then stand upright in order to remain in the sphere of the first light.