The encyclical Immortale Dei of Pope Leo XIII, Concerning the Christian Constitution of States (De Civitatum Constitutione Christiana), was issued November 1, 1885, during the time of the Kulturkampf in Germany, and the laicizing of schools in France.

It is a reaffirmation of ecclesiastical rights in which Leo deplored what he saw as a modern tendency to install in society the supremacy of man to the exclusion of God.

It is to the Church that God has assigned the charge of ... administering freely and without hindrance, in accordance with her own judgment, all matters that fall within its competence.

Man's natural instinct moves him to live in civil society, for he cannot, if dwelling apart, provide himself with the necessary requirements of life, nor procure the means of developing his mental and moral faculties.

Hence it is divinely ordained that he should lead his life, be it family, social, or civil, with his fellow-men, amongst whom alone his several wants can be adequately supplied.

"[9] "Nature and reason, which command every individual devoutly to worship God in holiness, because we belong to Him and must return to Him since from Him we came, bind also the civil community by a like law.

So, too, is it a sin in the State not to have care for religion, as a something beyond its scope, or as of no practical benefit ... All who rule, therefore, should hold in honour the holy name of God, and one of their chief duties must be to favour religion, to protect it, to shield it under the credit and sanction of the laws, and neither to organize nor enact any measures that may compromise its safety.

Were this not so, deplorable contentions and conflicts would often arise, and not infrequently men, like travellers at the meeting of two roads, would hesitate in anxiety and doubt, not knowing what course to follow.

To abdicate the field would allow those whose principles offer but small guarantee for the welfare of the State to more readily seize the reins of government.

[15] However, "it is unlawful to follow one line of conduct in private life and another in public, respecting privately the authority of the Church, but publicly rejecting it; for this would amount to joining together good and evil, and to putting man in conflict with himself; whereas he ought always to be consistent, and never in the least point nor in any condition of life to swerve from Christian virtue.