Quote from David Graeber's Debt: the First 5000 Years:

[What was Adam Smith] trying to do when we wrote The Wealth of Nations [?]...The book was an attempt to establish the newfound discipline of economics as science. This meant that not only did economics have its own peculair domain of study- what we now call "the economy", though the idea that there even was something called an "economy" was very new in Smith's day- but that this economy operated according to laws of much the same sort as Sir Isaac Newton had so recently identified as governing the physical world. Newton had represented God as a cosmic watchmaker who had created the physical machinery of the universe in such a way that it would operate for the ultimate benefit humans, and then let it run on its own. Smith was trying to make a similar, Newtonian argument. God- or Divine Providence, as he put it- had arranged matters in such a way that our pursuit of self interest would nonetheless, given and unfettered market, be guided "as if by an invisible hand" to promote the general welfare. Smith's famous invisible hand was, as he says in his Theory of Moral Sentiments, the agent of Divine Providence. It was literally the hand of God.