Summary of Leo XIII's Teaching on Religious Liberty

Liberty is “the highest of natural endowments”, and confers on man the dignity of having power over his actions (Libertas 1).  "[I]t is the faculty of choosing means fitted for the end proposed, for he is master of his actions who can choose one thing out of many" (Libertas 5).  Goodness is the end to which the will and its liberty are properly directed (Ibid).  “Liberty is a power perfecting man, and hence should have truth and goodness for its object” (Immortale Dei 32).  Liberty is only legitimate if it provides "a greater facility for doing good" (Libertas 42).

Liberty of worship in relation to the State is contrary to the State’s inherent duties (Libertas 21).  It is also contrary to justice (Libertas 21) and the virtue of religion (Libertas 19).  The State, like man, has a duty under the natural law to worship God (Immortale Dei 6).  A State violates this duty when it indiscriminately grants the same rights to false religions that it grants to the true religion (Libertas 21).  This is State godlessness, or ends in State godlessness (Ibid).  Moreover, it is contrary to reason for truth and error to have the same rights (Libertas 34).  

There is no natural right to religious liberty (Libertas 42), and Church concedes no right to anything except that which is true and honest (Libertas 33).  

States may, however, tolerate false religions to avoid a greater evil or to achieve a greater good (Libertas 33-34).  Evil is never to be desired for its own sake, and the common good is the only justification for a State to tolerate evil (Ibid).  

Sources

1.  Leo XIII, Libertas.  https://www.vatican.va/content/leo-xiii/en/encyclicals/documents/hf_l-xiii_enc_20061888_libertas.html

2.  Leo XIII, Immortale Dei.  https://www.vatican.va/content/leo-xiii/en/encyclicals/documents/hf_l-xiii_enc_01111885_immortale-dei.html