Guided by the perennial light of the Gospel and ever attentive to evolution of society, the Church's social doctrine is characterized by continuity and renewal133Cf. John Paul II, Encyclical Letter Sollicitudo Rei Socialis, 3: AAS 80 (1988), 515; Pius XII, Address to Participants in a Convention of the Catholic Action movement (29 April 1945), in Discorsi e Radiomessaggi di Pio XII, vol. VII, 37-38; John Paul II, Address at the international symposium “From Rerum Novarum to Laborem Exercens: towards the year 2000” (3 April 1982): Insegnamenti di Giovanni Paolo II, V, 1 (1982), 1095-1096.. It shows above all the continuity of a teaching that refers to the universal values drawn from Revelation and human nature. For this reason the Church's social doctrine does not depend on the different cultures, ideologies or opinions; it is a constant teaching that “remains identical in its fundamental inspiration, in its ‘principles of reflection', in its ‘criteria of judgment', in its basic ‘directives for action', and above all in its vital link with the Gospel of the Lord”134John Paul II, Encyclical Letter Sollicitudo Rei Socialis, 3: AAS 80 (1988), 515.. This is the foundational and permanent nucleus of the Church's social doctrine, by which it moves through history without being conditioned by history or running the risk of fading away. On the other hand, in its constant turning to history and in engaging the events taking place, the Church's social doctrine shows a capacity for continuous renewal. Standing firm in its principles does not make it a rigid teaching system, but a Magisterium capable of opening itself to new things, without having its nature altered by them135Cf. Congregation for the Doctrine of the Faith, Instruction Libertatis Conscientia, 72: AAS 79 (1987), 585-586.. It is a teaching that is “subject to the necessary and opportune adaptations suggested by the changes in historical conditions and by the unceasing flow of the events which are the setting of the life of people and society”136John Paul II, Encyclical Letter Sollicitudo Rei Socialis, 3: AAS 80 (1988), 515..
The Church's social doctrine is presented as a “work site” where the work is always in progress, where perennial truth penetrates and permeates new circumstances, indicating paths of justice and peace. Faith does not presume to confine changeable social and political realities within a closed framework137Cf. John Paul II, Encyclical Letter Centesimus Annus, 46: AAS 83 (1991), 850-851.. Rather, the contrary is true: faith is the leaven of innovation and creativity. The teaching that constantly takes this as its starting point “develops through reflection applied to the changing situations of this world, under the driving force of the Gospel as the source of renewal”138Paul VI, Apostolic Letter Octogesima Adveniens, 42: AAS 63 (1971), 431.. Mother and Teacher, the Church does not close herself off nor retreat within herself but is always open, reaching out to and turned towards man, whose destiny of salvation is her reason for being. She is in the midst of men and women as the living icon of the Good Shepherd, who goes in search of and finds man where he is, in the existential and historical circumstances of his life. It is there that the Church becomes for man a point of contact with the Gospel, with the message of liberation and reconciliation, of justice and peace. III. THE CHURCH'S SOCIAL DOCTRINE IN OUR TIME: HISTORICAL NOTES