I do not think there is any "maybe" to Pope's belief that we are all a small part of god's plan.
Christianity, in Pope's place and time, was an established and almost indubitable reality - though Pope, in a way, with his respect for reason, betokens the doubts that would destroy its power.
Now - I find I have not enough tie to read the thing, so I have collected a few commentariers on the poem for you - which I hope will aid you:
"The Essay on Man
Pope’s grand plan was not to write an epic as Milton did but to put together a series of verse epistles in the Horatian sense that would offer a moral critique of human behavior. The Essay on Man, which consists of four epistles, is about Man in general, not individual men. (And it’s mostly about male Men; women get little shrift in Pope’s philosophy.)
The first and third paragraphs on p. 2542 on the "Design" of the Essay on Man are very important to understanding the work. Pope is dealing with Man in the abstract, as He has been studied by scientific observation (the Royal Society method). Pope chooses to use verse because it is more elegant and memorable than prose.
Pope divides the first book of the poem into numbered verse paragraphs, which is helpful. In his opening he deliberately creates an imitation of Milton in vindicating, rather than justifying, the ways of God to Man. ¶1 introduces the concept of the Great chain of being. Pope’s argument is that all things have their place, and that we see echoes of God’s way of thinking in each level, though the echoes fade the lower we go. ¶2 notes where man falls in this great chain, and says that though Man is imperfect, that’s no bad reflection on God, who has a greater plan for us all that we mere imperfect mortals cannot always discern. See especially 69-72 for a statement about Man’s limitations. In ¶3, Pope points out that it is human nature to have hope for a particular fate rather than defer to God’s dispassionate judgment. See especially 87-90, 95, and 99.
In ¶4, Pope argues that pride—a significant moral weakness—is what leads Man to question God’s will. He defies rebellion in one very memorable couplet, 129-30. He does allow in ¶5 that some chaos is natural within Divine Order—esp. 168-70. And he argues in ¶6 that if man was meant to fly, God would have given him wings—see the funny couplets 193-96. ¶s 8 and 9 reiterate the notion of God the Great Designer and the importance of knowing (and staying in) our place in the Great Chain of Being as an act of moral obedience. There is a strong emphasis on submission to Divine Will—not on trying to change our state. Thus ¶10 is very important, especially its last couplet, 293-94.
You can see in this argument for accepting the status quo the roots of 18th century complacency. Don’t like your state? Don’t like how you are treated? No matter—you can’t tell why God has put you there. Just submit and enjoy it. This moral certainty—which some would definitely call smugness—leads to the toleration of slavery, of the denial of voting and other human rights, to the acceptance of workhouses and child labor, to a deliberate blindness to the needs of the poor and infirm—because "Whatever is, is RIGHT." Personally, it’s why I always want to smack Pope. But not everyone feels that way."
http://faculty.winthrop.edu/kosterj/ENGL201/popenotes.htm
here is another critique/explication:
http://www.literatureclassics.com/ancientpaths/pope.html
Here is a general discussion of Pope's life and poetry:
http://www.litencyc.com/php/speople.php?rec=true&UID=5169
Cliff notes - lots of info here:
http://www.cliffsnotes.com/WileyCDA/LitNote/id-50,pageNum-34.html
Here is Pope himself on Essay on Man, by the way:
http://www.theotherpages.org/poems/pope-i.html