We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.
This bold and attractive vision of human flourishing is articulated in the context of some very specific views of God, of humanity and the good life. Yet without this framework it's difficult to imagine anything less self-evident than the truth that "all men are created equal." If you divorce this conviction from its theological foundations, it's one of the most instantly falsifiable "self-evident" truths going! When you look at the mass of humanity born in such differing circumstances, with such differing opportunities and capacities, who on earth are the "we" who are able to see "equality" when all that's really "self-evident" is endemic inequality?
The answer is that the "we" who hold this vision of equality have soaked for long centuries in a view of God, the world and humanity which has been completely alien to the rest of thinking people.
Take Aristotle in Politics:
For that some should rule and others be ruled is a thing not only necessary, but expedient; from the hour of their birth, some are marked out for subjection, others for rule...
Aristotle took inequality to be the thing "self-evident." He repeatedly called slaves "living tools" and was quite comfortable with that arrangement. Same with Plato:
...nature herself intimates that it is just for the better to have more than the worse, the more powerful than the weaker; and in many ways she shows, among men as well as among animals, and indeed among whole cities and races, that justice consists in the superior ruling over and having more than the inferior. (Gorgias)
According to these brilliant pagan minds, equality is not taught by nature. The very opposite. Whatever "human nature" was, clearly some humans conformed closer to the ideal than others. So who could object if some were given more human "rights" than others?
The point is this: if observations of "nature" were all we had to go by, who on earth could disagree with the inequitable status quo? Of course nature produces more powerful and less powerful creatures, superiors and inferiors. If nature is our teacher why not endorse a class of rulers and a class of the ruled? Why not support the inequalities which nature clearly intends? Why fight it? On what grounds? With what justification? From where could you get an alternative vision of humanity? The only humanity we've ever observed has been one of profound inequalities!
Thus it seemed absolutely right to have a perilously steep hierarchy of being - the emporer at the top, the slaves at the bottom, with every subject knowing their place. Who could possibly object?
Except that the ancient Scriptures kept speaking of another way. The God who gets dirt under His fingernails forming humanity (Genesis 2), who wants to walk with His creatures in the cool of the day (Genesis 3). The Saviour who would fight for us and take the blow (Genesis 3:15). The Son who would give Himself in atoning death (Genesis 22). The LORD who is Servant and Sacrifice (see Isaiah 42; 49; 50; 53).
And then He comes to a humble "servant" (Luke 1:48) as a humble servant (Philippians 2:5-11). The whole pyramid is subverted as God becomes a Slave! And He becomes a Slave so that we, the slaves of sin and Satan, might become sons and daughters in His royal family. He descends to the depths and raises us to the heights so that now we might all feast at the same table - royals and commoners, masters and bond-servants.
And through this divine stooping, Christ shows us a radically different way of assessing "human nature." The Son "became flesh" - just common or garden humanity. He became a Jewish pauper with nothing in His appearance that we should desire Him (Isaiah 53:2). Whatever might be deemed "ideal humanity" had nothing to do with the properties inherent in it. The Man Jesus was valuable not because of the attributes of His humanity but only because the Son had chosen this flesh to be. Thus a Christian account of "human nature" does not look to the properties and capacities of particular persons but declares that humans as humans are inherently valuable. From there it's a hop, skip and a jump to declaring their "unalienable rights".
But wait - doesn't the bible (particularly the OT) endorse slavery? Well distinguish Hebrew slavery from Greco-Roman practice and distinguish both from the Trans-Atlantic slave trade of the 16th-19th centuries. Hebrew slavery was nothing like that which Wilberforce fought.
Certainly the Western mind has difficulty with the idea of selling oneself into slavery for a limited period (we prefer other forms of economic slavery), but those OT provisions were always temporary arrangements. In everyone's lifetime Jubilee was always just around the corner (Leviticus 25) - and the great hope was the Messiah who would bring ultimate and eternal liberation (Isaiah 61; Luke 4:16-21).
In the NT, Paul counselled slaves (in this new Greco-Roman context) to seek their freedom if they could (1 Cor 7:21-24) and declared slave-trading to be sinful (1 Tim 1:10) thereby cutting the jugular of the whole practice. But really, it was the intellectual revolution of the gospel that was so much more subversive than any 'revolt of the slaves' could be.
And it's a revolution that we need to continue today. It's estimated that there are 27 million slaves in the world right now and so often it is Christians who continue to be at the forefront of the fight against human-trafficking. Why? Because Christians actually have an anthropology that treats each human with "unalienable rights" rather than as "living tools". Anyone who seeks to take some high-ground on the issue of slavery must produce an account of human nature that will actually protect the weak and the vulnerable from being used. But on what grounds will they justify such a stand?
I live in a country that kills 200 000 of the weakest members of our species every year because of the will of the strong. Our culture can claim no high ground in protecting the "unalienable rights" of all people. We have our own hierarchies based on the properties and capacities of individuals and we discriminate with extreme prejudice. If we want real equality we must return to the only true foundation: the Master who became Slave.