The key challenge and goal of history is to determine the true causes of past events so as to inform our actions in the future. The problem is that there is always so much going on in any historical moment, so much that is unique, that it's difficult to come up with generalized principles which apply in different historical circumstances. To overcome this problem, a simplified theory of history is needed to filter out important data to focus on when analyzing historical trends. Modern historians use a variety of different lenses through which to analyze history, whether that be by focusing on the relationship between classes, technological advancements, or the competition between peoples and nations as the driving force behind the development of societies. The comminality between all these historical worldviews is that they are all essentially amoral, emphasis is placed on evolutionary/historical trends and less on the moral choices of peoples and leaders. This is in stark contrast to ancient historians, whose history was almost always highly moralistic in tone and who tended to attribute misfortune to the moral failings of the people or of their leaders. This neglected historical worldview merits closer examination to discover the influence of moral character on the development and trajectory of societies.
There is a saying that character is destiny, ie, that the character traits of an individual, such as honesty, bravery, integrity, etc. often heavily determine their future. The same principle also holds for larger entities. For families, for example, one can hold that the moral character of the parents is likely the key factor that determines the success or faliure of the family. If the parents are honest, selfless, faithful, then the foundations of the family are secure. The same principle holds for larger organizations and companies where the moral force and character traits of a handful of individuals in the community (especially the founder) has a massive influence on the development of the organization and ultimately determines the company/organization's success or faliure. One can argue that the same principle also extends to even larger entities, that the development of a nation or society, which at the end of the day is only a collection of many families and organizations, is deeply linked to the traits and habits of its people.
This becomes even more clear when one considers limiting cases ... if every citizen of a nation overnight became slothful, then no work would get done and the economy of a country would immediately collapse. If all citizens became cowards, than they would soon be conquered by their neighbors, if they became unjust, then law would breakdown and society would begin to collapse. One can imagine that different societies have these traits to different degrees and that the prevalence of those traits affects the development of society (If society A is double as courageous as society B, then its development will be dramatically different). There is strong resistance to this type of thinking in the modern world because it implies that different societies can differ morally, and can have character traits just as individuals have traits, ie it implies that societies can be morally better with respect to some traits than other societies. The evidence supports that a society's culture often leans towards certain virtues and away from others. To illustrate this, consider one essentially moral problem in the modern world, corruption. Those who have traveled to countries where corruption is rampant will understand that at least with respect to this one trait, societies very extremely dramatically! Moreover, a historical analysis of societies, will show that societies, much like individuals, can exhibit moral growth or decline, depending on cultural influences and societal norms.
If then the general principle is accepted that the morality of individuals in society highly affects its development (and indeed affects its development more than any other factor), then the main challange becomes how to apply this principle to historical analysis. How does one measure the virtues of a people? Here I propose a solution. Imagine first making up a battery of questions to measure the prevalence of certain desirable traits in a community. Much like personality tests, these societal morality tests (SMT) should be carefully constructed to measure how widespread different virtues are in the population. For instance, one question to measure the moral virtue of courage can ask if the average member of the population would risk their life to save a stranger in distress? This and similar questions like it can be used to get a rough idea of the character of a society.
After composing such a test, the challenge will be to apply the test to the past. Unfortunately, for most times and places, historical accounts have focused on the lives and habits of the rulers and have neglected to document the habits, feelings, and behaviors of the ordinary population. How can one extract out the moral traits of societies from the few accounts of individuals that have made their way down to us? This task can be accomplished, by assuming that the rulers of a society are ultimately molded by the same societal forces as the rest of the population. Therefore, the handful of public personalities in an age can be taken as a representative random set of individuals from that era of history, and from their personalities one can extrapolate out the character of the general populace. For example the presence of Julius Caesar, Cicero, and Pompey around 50 BCE reflects the adventurism and ambition which characterized that age, while the characters of Nero and Caligula in the first century CE demonstrates the sensuality and a brutality of their time.
For some historical periods, this method of relying on the characters of the most well know public persons can be supplemented with direct data from ordinary people whether in the form of preserved letters, or in the more recent past, with television shows, music, and social media/internet activity. This information can be probed and analyzed to extract out a far more accurate view of the morals and habits of the people. In fact, the advent of the internet, is a defining milestone for the field of history on par with the advent of writing ... a moment when data on the past expands a thousand fold. Future historians will be able to piece together infinitely more about us, than we can of past generations and history as a field of study will likely become much more scientific and much more accurate.
Relying therefore on a thorough analysis of the characters of the public persons of an age and on any direct information from the lives of ordinary people that survive, the morality of a people can be extracted using a well constructed SMT and the effects of the moral habits of peoples can be studied. With the advent of big data, this process can become much more quantitative and systematic allowing us to compare the virtues and moral characters of different societies and even to highlight the morals to cultivate to promote the prosperity of a given society.