Eternal recurrence? The inevitable decline of everything?
Indeed, all things are temporary. And the human capacity for self-deception is unlimited.
Life is precious & true Love so very rare. Revere these things. They make us fully human.

And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
² That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.
³ And the Lord said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years.
⁴ There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.
⁵ And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.
⁶ And it repented the Lord that he had made man on the earth, and it grieved him at his heart.
⁷ And the Lord said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
⁸ But Noah found grace in the eyes of the Lord.
 --Genesis 6:1-8; King James Version (KJV)

 
“I am the wisest man alive, for I know one thing, and that is that I know nothing.” 
“The society we have described can never grow into a reality or see the light of day, and there will be no end to the troubles of states, or indeed, my dear Glaucon, of humanity itself, till philosophers become rulers in this world, or till those we now call kings and rulers really and truly become philosophers, and political power and philosophy thus come into the same hands.” 

―  Plato, The Republic 

The boast of heraldry, the pomp of pow'r,
And all that beauty, all that wealth e'er gave,
Awaits alike th'inevitable hour.
The paths of glory lead but to the grave.
--Thomas Gray, 'Elegy Written in a Country Churchyard'

"...[O]ne thing seems certain - that nothing certain
exists and that there is nothing more pitiful or more presumptuous than
man."
"Because of a curious disease of the human mind, it pleases us to
enshrine in history records of bloodshed and slaughter, so that those ignorant
of the facts of the world may become acquainted with the crimes of
mankind."
--Pliny the Elder, Natural History

 
With The Course of Empire, Thomas Cole achieved what he described as a "higher style of landscape," one suffused with historical associations, moralistic narrative, and what the artist felt were universal truths about mankind and his abiding relationship with the natural world. In a letter to his patron Luman Reed, Cole wrote enthusiastically of an idea for his first large-scale allegorical series:

A series of pictures might be painted that should illustrate the History of a natural scene, as well as be an Epitome of Man—showing the natural changes of Landscape & those effected by man in his progress from Barbarism to Civilization, to Luxury, the Vicious state or state of destruction and to the state of Ruin & Desolation.

The philosophy of my subject is drawn from the history of the past, wherein we see how nations have risen from the Savage state to that of Power & Glory & then fallen & become extinct... ¹

Reed accepted the artist's proposal, and Cole worked on The Course of Empire for the next three years. The five paintings were specifically designed for a prominent spot in Reed's third floor picture gallery in his New York City mansion at No. 13 Greenwich Street. See Cole's  Installation Diagram for the Course of Empire. They chart the course of human civilization, while at the same time progressing through different times of day and various weather conditions, reflecting man's changing relationship to his environment.
A trip to Europe (1829-32) deeply influenced Cole's work. There he first saw the ruins of ancient civilizations, remnants of a past time that could not be found in America. See After Giovanni Battista Piranesi, The Colosseum. The Course of Empire also reflects the growing interest in ancient history among the elite. The title of the series derives from a well-known eighteenth-century poem by the British philosopher Bishop George Berkeley (1685-1753), entitled "Verses on the Prospect of Planning Arts and Learning in America" (1726). The poem alludes to five states of civilization and the implicit prophecy that America would prove to be the next great empire. Cole also read Lord Byron's 1818 work, Childe Harold, (see J.M.W. Turner, Childe Harold's Pilgrimage) and cited these lines in regard to his series:

There is the moral of all human tales;
  'Tis but the same rehearsal of the past.
  First Freedom and then Glory—when that fails,
  Wealth, vice, corruption—barbarism at last.
  And History, with all her volumes vast,
  Hath but one page. ²

Cole's contemporary, novelist James Fenimore Cooper, marked the success of the allegorical series when he wrote in 1849, "Not only do I consider the Course of Empire the work of the highest genius this country has ever produced, but I esteem it one of the noblest works of art that has ever been wrought." ³   See John Wesley Jarvis, Portrait of James Fenimore Cooper.
Cole's words:

I have had some difficulty in finding a comprehensive & appropriate title for the series of pictures which I am now painting for Mr. Reed. I have had several but have discarded all of them; but now I think I have a good one. Although it may perhaps be considered lofty & ostentatious[,] it is The Course of Empire." ⁴
I have been dwelling on many subjects, and looking forward to the time when I can embody them on the canvas. They are subjects of a moral and religious nature. On such I think it the duty of the artist to employ his abilities: for his mission, if I may so term it, is a great and serious one. His work ought not to be a dead imitation of things without the power to impress a sentiment, or enforce a truth. ⁵

 
http://www.explorethomascole.org/tour/items/63/series/

Thomas Cole (February 1, 1801 – February 11, 1848) was an English-born American artist. He is regarded as the founder of the Hudson River School, an American art movement that flourished in the mid-19th century. Cole's Hudson River School, as well as his own work, was known for its realistic and detailed portrayal of American landscape and wilderness, which feature themes of romanticism and naturalism.^[1]

http://en.wikipedia.org/wiki/Thomas_Cole