Envision a locomotive the way many would circa 1860. What technology! It wasn’t brand new (as they were invented in 1804) but it was a Monster of the age in terms of making the world move. 

Tolstoy envisions the locomotive as a symbol of great historical movements and uses this symbolism to describe the limitations historians face in finding causes for such movements. 

He posits three people viewing the mighty locomotive and trying to explain the cause of the movement. 

The first, Tolstoy deals with a simple peasant. The man is overawed by the train and thinks the Devil (or some divine force) makes it move. With no understanding of mechanics, he concludes that something beyond man is at play. That is all the simple man needs for an explanation.  Tolstoy doesn't discount this view out-of-hand. Instead, he finds as much value in this posture as with more scientific thinkers. 

The second hypothetical person looking at the locomotive is a more sophisticated and inquisitive type from the Age of Enlightenment. He sees the wheels moving and estimates that is the cause.  Like historians looking for the cause of a great event, the inquisitive man is attempting to break down possible causes of the train's movement but can not get at it with any efficiency. Instead, he only finds a piece of the puzzle. If he studies the matter long enough, he may also discover that the pressure of steam in the boiler is another cause. However, one can continue the exercise infinitely through asking what process generates steam and so on. Basically, the inquisitor will go from cause to cause and pick ones that stand out to him while neglecting ones just as valid. Tolstoy is trying to exemplify the limited analysis historians often perform. 

The third hypothetical observer notices awe-inspiring black smoke rising out of the train’s chimney.  Seeing such a powerful manifestation, perhaps for the first time, this person may wrongly attribute the “cause” of the train's movement to something that stands out. Tolstoy is making the point: historians can mistake byproducts for causes.  

Tolstoy believes it is theoretically possible that some super-intelligence could see the big picture and know all the reasons for events. In other words, this all-seeing-eye could see everything that every happened at every point in history. But as to human capability, our vision only goes so far. 

Tolstoy describes that we generally describe the force that compels men to do something as “power,” but that word does not do the concept justice. One of his goals is to further explore "power" in this Epilogue. He believes a great deal of the "power" that makes our world move it is not understood. The same reasoning applies to movements of people. The causes are complex and often inaccessible. 

Tolstoy compares the process of trying to understand history to the types of money in circulation – paper money, metal coins and gold. He feels that most efforts of historians can be compared to paper money; not worth their weight and fungible. People may believe certain theories; but that is because of their Faith in a certain currency and not because of any true value of the theory. 

Gold is what Tolstoy seems to have stumbled upon in writing War & Peace. He gets to the essence of power through creating fictional characters symbolizing how each level of society reacted to the Napoleonic wars in a way that has stood the test of time. The second half of the19th century was a time of great consideration of metaphysics and Tolstoy was an essential part of that Locomotive.