In a recent Vortex, host Michael Voris made mention of Pope Leo XIII's encyclical on Christians as Citizens, Sapientiae Christianae.
Though written in 1890, the encyclical is relevant today. From the first paragraph:
"From day to day it becomes more and more evident how needful it is that the principles of Christian wisdom should ever be borne in mind, and that the life, the morals, and the institutions of nations should be wholly conformed to them. For, when these principles have been disregarded, evils so vast have accrued that no right-minded man can face the trials of the time being without grave anxiety or consider the future without alarm. Progress, not inconsiderable indeed, has been made towards securing the well-being of the body and of material things, but the material world, with the possession of wealth, power, and resources, although it may well procure comforts and increase the enjoyment of life, is incapable of satisfying our soul created for higher and more glorious things. To contemplate God, and to tend to Him, is the supreme law of the life of man. For we were created in the divine image and likeness, and are impelled, by our very nature, to the enjoyment of our Creator. But not by bodily motion or effort do we make advance toward God, but through acts of the soul, that is, through knowledge and love. For, indeed, God is the first and supreme truth, and the mind alone feeds on truth. God is perfect holiness and the sovereign good, to which only the will can desire and attain, when virtue is its guide."
The encyclical can be read online at a number of sites, including the Vatican website and here.
I don't particularly like reading documents online, so I've put the encyclical into pdf format and mobi for Kindle and made both available for downloading.