Is the atheist a fool?
Scripture has much to say about the fool, especially in its Hebrew poetic and wisdom literature. Proverbs paints the picture of a fool as one who shuns wisdom and will not listen to instruction. The fool rejects any kind of discipline and even gloats about his folly. The fool despises God, who is the source of wisdom and knowledge, and shows Him no reverence. There is no fear of the Lord God before the eyes of the fool.
Proverbs 1:7 The fear of the LORD is the beginning of knowledge; Fools despise wisdom and instruction. (NASB)
Proverbs 14:15 The naive believes everything, But the sensible man considers his steps. (NASB)
Proverbs 17:7 Excellent speech is not fitting for a fool, Much less are lying lips to a prince. (NASB)
Proverbs 1:22 "How long, O naive ones, will you love being simple-minded? And scoffers delight themselves in scoffing And fools hate knowledge? (NASB)
Proverbs 28:4 Those who forsake the law praise the wicked, But those who keep the law strive with them. (NASB)
Proverbs 18:2 A fool does not delight in understanding, But only in revealing his own mind. (NASB)
Psalm 14:1 For the choir director. [A Psalm] of David. The fool has said in his heart, "There is no God." They are corrupt, they have committed abominable deeds; There is no one who does good. (NASB)
Psalm 53:1 For the choir director; according to Mahalath. A Maskil of David. The fool has said in his heart, "There is no God," They are corrupt, and have committed abominable injustice; There is no one who does good. (NASB)
The passages above are only a small portion of all of the things Scripture states about the fool but they are sufficient to reveal much of the character of the fool. The term "fool" in Scripture describes a particular type of person, it is not just an instance of empty name calling. The fool turns away from the fear of the Lord and finds him or herself enveloped by futility in thought, word, and deed.
In the last two passages we are told that the fool says in his heart, "There is no God". Recognize that when this was penned, there was no idea of a "general theism" or other such nonsense. When the Bible speaks of God, it means the God of the Bible, not some general theistic god found at the end of a philosophical proof. This means that while the atheist is certainly a fool by biblical standards, so are all others who constantly hold the truth of God down and seek after themselves, becoming corrupt and practicing injustice according to their lack of a tenable worldview.