I admire Kipling for many of the same qualities that so many inhabitants of our modern civilization dislike him.   He stood for unabashed masculinity, the British Empire, and pride in British inspired civilizations such as America, the nation that was eventually to supplant Britain in world dominance.  To me he stood for qualities which are rapidly vanishing in our modern society; self reliance, patriotism, the virtues and values of Judeo-Christian morality, faith in your fellow man, the ability to tell right from wrong and good from evil, and the self confidence to stand up to those who's self indulgence and narcism 

Pacifism become popular, patriotism unpopular, and religious beliefs and their attendant morality had suffered a serious setback.  Jesus' statement on the cross "My God, My God, why have you forsaken me?" was reinterpreted to mean "What sort of God would allow this to happen?".  This lead to a generalized rejection of traditional morality and social values among large numbers of people, especially the national elites.

The first Russian revolution had deposed the Tsar in 1917, and many people began to look towards Marxist socialism as the ultimate solution to the world's problems.  It made sense at the time.  Marxist socialism had never been tried on a large scale before.  It's emphasis on rationalism and the rejection of God and his attendant  religious values appealed to the educated elites who tended to resent religion as an imposition that interfered with their own pursuit of "happiness". 

Marxist socialism appealed to the lower strata of society as well.  Socially acceptable hedonism combined with "free money" from the state would appeal to everyone except those who clung to religion as their source of solace and social cohesion! 

The massive failures of all the great socialist experiments lay well in the future.  Communism (international socialism) and Fascism (national socialism) were in their infancy, and Nazism (racially defined national socialism) in Germany arose as an outgrowth of Fascism after 1919.  Progressivism, which advocates the gradual replacement of traditional democracy with socialist values and laws began in the US in 1912 with the election of Theodore Roosevelt. 

The zeitgeist of the day therefore became a stew of Marxism and the abandonment of traditional values by a sexually liberated "popular culture" (think the "roaring twenties") in many of the most prosperous countries. 

It was against this background that Kipling wrote his poem, "The Gods of the Copybook Headings".  He was well ahead of his time in doing so.  Kipling recognized that the abandonment of the morals and values that created the British empire would lead not only to the downfall of the empire itself, but the eventual downfall of the civilization that it had created.  A people who had abandoned their moral values would eventually abandon each other.  They would abandon honesty, and without honesty there would be no reason to trust anyone else.  Without sexual morality, the traditional social contract based on trust between the sexes would vanish, and the people would eventually abandon marriage.  Without marriage, the family, the most basic unit of any civilization would wither and die.  Money would become the holy grail, and people would stoop to any depths to get it.  At the top, leaders would betray their institutions and their countries, impoverishing virtually everyone else to get rich themselves.  At the bottom, gangs of thugs would roam the streets stealing anything of value. 

Kipling knew that the abandonment of the values that built the civilization would lead to its destruction.  He also knew that as the destruction settled in on the civilization, the old values would resurface, probably with a vengeance.  This is the meaning of his poem, "The Gods of the Copybook Headings".

Unfortunately, few children (and few adults) today have any idea of what these proverbs mean or why each one is the doorway to a concept of basic morality and values that used to be universal in our society. In those days, common knowledge of these concepts acted as a glue that held society together and placed moral limits on an individual's behavior.  Even if they all had cell phones, no kid in those days would dream of joining a "flash mob" to rob or assault innocents.  They would all know from early childhood that "if you don't work, you die", and "the wages of sin is death"!  These are just a few of the moral truths that were taught to all children in those days, and they were known and understood by the poorest members of society as well as the richest.

"Cambrian measures and Carboniferous Epoch" are both acknowledgements that materialistic values are ancient, and have always been with us.

"Feminian Sandstones" has no modern definition, but refers, like Cambrian measures, to the ancient origin of materialism.  It was probably a phrase thought up by Kipling because it sounds ancient.

There are only four things certain since Social Progress began —
That the Dog returns to his Vomit and the Sow returns to her Mire,

The dog and the sow represent base instinct, the very source of material values. The origin of The Gods of the Marketplace. 

Albert Einstein once said "The definition of insanity is doing the same thing over and over again and expecting different results."  John Adams once said, "There never was a democracy yet that did not commit suicide."  Kipling said that a fool refuses to learn from past failures. 

The "Brave New World" was the phrase chosen by Aldous Huxley for the title of his  famous 1932 novel about a dystopian future society.  This was exactly what Kipling meant when he coined the phrase! 

This was a slap at Marxist/Materialist values, a welfare state in which all people are paid for existing, and morality is forgotten.  In other words, a society that worships at the alter of materialistic values. 

Throughout history, we have watched the cycle of civilizations based on moral values rise, and then fall into bloody chaos as the culture deserts those moral values.  And after the fall, all is dark until moral values reassert themselves and allow for the usually violent dismantling of the old order and the rebuilding of a new civilization.