Does the State have a fundamental duty to the true Church of Christ? That is the question at the heart of integralism. I wrote a long article about this question for Chronicles Magazine, but it can be answered briefly.
In Humanum genus, Leo XIII warned about the dangers of Freemasonry. They think 'the teaching office and the authority of the Church should be of no moment in civil society.' So they 'preach to the populace and contend that sacred affairs ought to be entirely separated from civil affairs.’
The Church and the State are both moral bodies that are complete and independent within their own spheres. But they aren’t equal or separate. The benefits man gets from civil society are for the quest the Church sets him. So the natural is subordinate to the supernatural.
The Church has no direct power over the State in matters that are within the competence of the State. Although Christ is ultimately the monarch of all civil societies, He promised Peter only the keys to the heavenly kingdom. His kingdom is ‘not of this world.’
But there is only one supreme good that is the aim of a successful human life: the beatific vision, enjoyed with the Church triumphant. So all human activity, social as well as individual, must be referred to that. And the State must defer to the Church in spiritual matters.
The Catholic Church has an actual and sovereign God-given right to preach to all the nations of the world and establish itself among them. It has this right because God obliges all men to accept its teaching. Anyone working against the Church is working against God.
The Church cannot be ignored or treated as equal to religious societies not authorised by God. And the Church cannot ‘be so unfaithful to its office as to dissemble with regard to what is false or unjust, or to connive at what is hurtful to religion’ (Leo XIII).
Since individual human beings have a duty to acknowledge Christ in all their activity, so does civil society. It's a company of individual human beings. And only the Catholic Church offers us fellowship with Christ. So any individual of society not acknowledging it is bad.
The Catholic Church has the right to the support of the State because it’s the only supernatural society established by God. The State should discourage any offence against it. Uttering a falsehood in speech or in writing is evil. Error has no rights.
The State cannot force anyone into the Church. That is an affront to both man and God. But #15 in the Syllabus of Errors is that ‘a man is free to embrace and profess the religion which, led by the light of reason, he shall have thought to be true.’ There's no such freedom.
Leo XIII warned that
‘it is a crime for the State to act as if there were no God…Liberty is...legitimate only in so far as it affords greater facility for doing good, but no farther…False freedom in the matter of worshiping God...is necessarily an evil thing.’
Because liberalism makes freedom an end in itself rather than merely a means, it’s teaching the West this the hard way.