We must add, therefore, that it is in the nature of the common good that every single citizen has the right to share in it—although in different ways, depending on his tasks, merits and circumstances. Hence every civil authority must strive to promote the common good in the interest of all, without favoring any individual citizen or category of citizen. As Pope Leo XIII insisted: "The civil power must not be subservient to the advantage of any one individual, or of some few persons; inasmuch as it was established for the common good of all." 40Leo XIII's encyclical letter Immortale Dei." Acta Leonis XIII, V, 1885, p. 121. Nevertheless, considerations of justice and equity can at times demand that those in power pay more attention to the weaker members of society, since these are at a disadvantage when it comes to defending their own rights and asserting their legitimate interests. 41Cf. Leo XIII's encyclical letter Rerum novarum, Acta Leonis XIII, XI, 1891, pp. 133-134.
In this connection, We would draw the attention of Our own sons to the fact that the common good is something which affects the needs of the whole man, body and soul. That, then, is the sort of good which rulers of States must take suitable measure to ensure. They must respect the hierarchy of values, and aim at achieving the spiritual as well as the material prosperity of their subjects.42Cf. Pius XII's encyclical letter Summi Pontificatus, AAS 31 (1939) 433.
These principles are clearly contained in that passage in Our encyclical Mater et Magistra where We emphasized that the common good "must take account of all those social conditions which favor the full development of human personality.43AAS 53 (1961) 417.