Why the unusual spelling of aTheist? You grammarians know about the alpha privative. When something is atypical, it means "not typical." For instance, 'that comment was atypical of her.' In other words, she doesn't usually say things like that. A boulder is amorphous. It is not round like a beach ball or cubical like a box. Providence has morphed it into an asymmetrical shape.
The point being, should we give aTheism the dignity of a capital letter? Theists are people who recognize God's existence, and some Theists are also children of THEOS (God, in Greek) by His grace in Jesus. But the aTheist denies THEOS, Who surely deserves the minor honor of capitalization. But on to our analogy…
A Christian was out for a walk on a beautiful day. There was not a cloud in the sky. In fact it was so sunny that he was wearing his darkest sunglasses. Suddenly he came upon a strange sight. It was his neighbor, waving a flashlight up and down, here and there!
"My, my neighbor," said the believer. "What on earth are you doing?"
"I am trying to discover whether or not the sun exists," he replied.
The Christian was surprised to say the least, and wondered at the sanity of his neighbor. "Why, the sun is giving you the light to see everything around us! You don't need that flashlight to see anything. What do you mean?"
The neighbor replied, "Unless I can see it with my own eyes, with the help of my flashlight shining on it, I won't believe that the sun exists!"
That's what the aTheist is like.
"…The heavens declare the glory of God, and the sky above proclaims his handiwork." (from Psalm 19)
"Where shall I go from Your Spirit? Or where shall I flee from Your presence? If I ascend to heaven, You are there! If I make my bed in Sheol, You are there!" (Psalm 139:7,8)
"For His invisible attributes, namely, His eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse." (Romans 1:20)
The aTheist is not an honest seeker for the truth, using observation and reason (the flashlight stands for that) to search out the existence of THEOS. According to God's word, the certainty of His existence surrounds us all.
And this is not merely an academic question. Just as the flashlight wielder could not look directly at the sun without harm, the sinner outside of Christ cannot bear the presence of his Creator and Judge without eternal harm.
"…The fool says in his heart, 'There is no God.' They are corrupt, they do abominable deeds; there is none who does good." (from Psalm 14)
The aTheist is not an innocent searcher, but rather a self-deceived fool!