In his famous book, The Existence and Attributes of God, Puritan Stephen Charnock tells us, "By the nonregarding [sic, for "disregarding"]of God, men rush into evil. Pharaoh oppressed Israel because he knew not the Lord. If he did not deny the being of a deity, yet he had such an unworthy notion of God as was inconsistent with the nature of a deity: he, a poor creature, thought himself a match for the Creator." He refers to the passage in Exodus known especially for the account of the ten plagues, as Moses tried to free the Israelites from slavery in Egypt. In that passage, we see comments from Pharaoh like, "Who is the Lord that I should obey His voice and let Israel go?" (Genesis 5:2).
Charnock called this attitude "practical atheism." He notes that Pharaoh never denied the existence of gods, or even of the God. Rather, Pharaoh denied the sovereignty of God, asserting, instead, his personal autonomy from the will and commands of God. That is why Charnock calls Pharaoh's mentality "atheism," because it was a denial, in effect, of the deity, of the Godness, of God.
This exemplifies, Charnock continues, the attitude behind all the sins of men, whether or not stated explicitly as it was by Pharaoh. It is, in fact, the false promise made by Satan in the Garden, that Adam and Eve would become like gods, deciding for themselves what is good and what is evil (Genesis 3:5). It is as if he told them, "Forget about God and decide for yourselves." And, like Pharaoh long after them, they accepted the promise of Satan.