"Abba! Father!'" (Rom 8: 15). What does this mean?
St Paul presupposes the social system of the ancient world in which slaves existed. They owned nothing, so they could not be involved in the proper development of things.
Co-respectively, there were sons who were also heirs and were therefore concerned with the preservation and good administration of their property or the preservation of the State. Since they were free, they also had responsibility.
Leaving aside the sociological background of that time, the principle still holds true: freedom and responsibility go hand in hand. True freedom is demonstrated in responsibility, in a way of behaving in which one takes upon oneself a shared responsibility for the world, for oneself and for others.
The son, to whom things belong and who, consequently, does not let them be destroyed, is free. All the worldly responsibilities of which we have spoken are nevertheless partial responsibilities for a specific area, a specific State, etc.
The Holy Spirit, on the other hand, makes us sons and daughters of God. He involves us in the same responsibility that God has for his world, for the whole of humanity. He teaches us to look at the world, others and ourselves with God's eyes. We do not do good as slaves who are not free to act otherwise, but we do it because we are personally responsible for the world; because we love truth and goodness, because we love God himself and therefore, also his creatures. This is the true freedom to which the Holy Spirit wants to lead us.
The Ecclesial Movements want to and must be schools of freedom, of this true freedom. Let us learn in them this true freedom, not the freedom of slaves that aims to cut itself a slice of the cake that belongs to everyone even if this means that some do not get any.
We want the true, great freedom, the freedom of heirs, the freedom of children of God. In this world, so full of fictitious forms of freedom that destroy the environment and the human being, let us learn true freedom by the power of the Holy Spirit; to build the school of freedom; to show others by our lives that we are free and how beautiful it is to be truly free with the true freedom of God's children.
[Pope Benedict, Vigil 3 June 2006]