What sets the ancient and modern worlds apart? As I suggested a couple of days ago, the explanatory successes of natural science might be offered as an explanation. My take on the situation, however, is that the successes of natural science are a by-product of an intellectual revolution, through which the world has quite literally been turned inside out.
The short version of the story goes something like this: We no longer look up and wonder who or what is looking down on us. We no longer wonder about the standard against which our actions will be measured. We now look down on ourselves from an artificial distance. We cut ourselves into tinier pieces. We plug into flowcharts, diagrams, and pie graphs. And we chide ourselves for thinking someone or something might have been doing the same.
In the process of the world being turned inside out, the fundamental categories of truth change. Ancient religious texts delving into the question the origin of all things invited readers or hearers to measure themselves against an infinite moral standard. The human being lived a life of bodily limitations, which ended with bodily death. What do to with that life, how to relate to other human beings, other living beings, other things, required answers. Some sort of account of how everything fit together, the way things are--which informed how human beings acted, and so was also the way things ought to be--was needed.
The modern scientific enterprise changes both the means and ends of inquiries into the truth of things. Reference to the origin of all things drops away entirely. Instead of wondering about how humanity related to the world around them, people pay much closer attention to how things interacted with each other. Standards of measurement were developed that quantified, multiplied, and formulated. Fact and value, the way things are and the way things ought to be, were held at a theoretical distance from each other.
The easiest way to illustrate the difference between ancient and modern is to consider how motion was understood. The Greek philosopher Aristotle provides the basic framework in which to understand the motion of physical objects down to the 15th century with the heliocentrism of Copernicus and Galileo's theory of inertia and the motion of living beings down to the 19th with Darwin's account of the origin of species. Aristotle held that everything, living or not, natural strove towards a state a of 'rest'. A falling rock seeks the earth. A plant seeks to realize the potential of its species. So also do animals and human beings. Only when a things innate potentials were realized was rest achieved.
In such a world, everything possesses moral significance because everything, each in their own ways, strives to achieve the same thing. The entire natural order is also thoroughly moral. The heavens speak the glories of God, and, as a consequence, the impotence of the human being to accomplish anything lasting. The natural order provides example for human action. The love of a mother bird bears her chicks shows the human mother the sort of devotion God requires her to bear towards her children. The orderly progress of sun in the sky, ruling over life on earth, provides a standard for the just rule of kings and princes who govern the polity.
Sometime in the 14th century, however, late medieval thinkers wondered about the relationship between velocity and acceleration of objects. If it was possible to determine how fast an object was going (velocity = distance/time), was it also possible to determine how fast an object was speeding up (acceleration = velocity/time)? With the advantage of the accumulated wisdom of generations, we see a very simple mathematical relationship between velocity and acceleration. Late medieval thinkers lacked that advantage.
A couple of assumptions were acquired. First, that the observable world was governed an intelligible order, in which things could be expected to behave with a lawful regularity. And second, that the regularity in the natural order was quantifiable. The first assumption very easily meshed with a belief in a Creator God, whose existence guaranteed the lawful regularity in the observable world. The second was problematic, as the enumeration of things does not necessarily yield a moral lesson, which Aristotelian thinkers had been accustomed to find in the natural order. To determine something is traveling at 10 m/s or accelerating at 2 m/s2 doesn't yield a morally significant answer, even though it may aid in the development of ever more accurate and more powerful artillery, which can be employed to rain death fro above on civilian populations that previously had been safe behind city walls.
And so a crack formed in the system of human knowledge. One could argue the crack had always existed, that distinctions between faith and reason, or soul and body attested to the same thing. What was different, however, was that thinkers began to experiment with the idea of studying the natural world 'for its own sake' without immediate moral reference to the origins and ends of all things. St. Jerome's translation of the creation narratives in Genesis had God say, 'Fiat lux', or 'Let there be light'. Henceforth thinkers would increasingly operate in a world in which God's light proceeded from two clearly distinct sources, illuminating very different truths about the way things are, only one of which seemed to have anything to say about the way things ought to be. Copernicus' heliocentrism and Darwin account of the origin of species are both consequences of this fundamental division of knowledge.