Pope Francis - On Idolatry, from 'Lumen Fidei'

Martin Buber once cited a definition of idolatry proposed by the rabbi of Kock: idolatry is "when a face addresses a face which is not a face".[10] In place of faith in God, it seems better to worship an idol, into whose face we can look directly and whose origin we know, because it is the work of our own hands. Before an idol, there is no risk that we will be called to abandon our security, for idols "have mouths, but they cannot speak" (Ps 115:5). Idols exist, we begin to see, as a pretext for setting ourselves at the centre of reality and worshiping the work of our own hands. Once man has lost the fundamental orientation which unifies his existence, he breaks down into the multiplicity of his desires; in refusing to await the time of promise, his life-story disintegrates into a myriad of unconnected instants. Idolatry, then, is always polytheism, an aimless passing from one lord to another. Idolatry does not offer a journey but rather a plethora of paths leading nowhere and forming a vast labyrinth. Those who choose not to put their trust in God must hear the din of countless idols crying out: "Put your trust in me!" Faith, tied as it is to conversion, is the opposite of idolatry; it breaks with idols to turn to the living God in a personal encounter. Believing means entrusting oneself to a merciful love which always accepts and pardons, which sustains and directs our lives, and which shows its power by its ability to make straight the crooked lines of our history. Faith consists in the willingness to let ourselves be constantly transformed and renewed by God's call. Herein lies the paradox: by constantly turning towards the Lord, we discover a sure path which liberates us from the dissolution imposed upon us by idols.

From: LUMEN FIDEI, Ch.13 - http://www.vatican.va/holy_father/francesco/encyclicals/documents/papa-francesco_20130629_enciclica-lumen-fidei_en.html