The first part of Gaudium et Spes, entitled “The Church and Man's Vocation,” discusses four main themes in four chapters: the dignity of human beings, the community of mankind, human activity, and the Church's role in the modern world.
Here are a few topics and ideas you'll find in Part I, Chapter I, of Gaudium et Spes.
Part One – The Church and Man's Vocation
We Must Respond to the Promptings of the Holy Spirit
* The Holy Spirit allows the people of God to see the world in the light of faith, to grasp God's ideal for humanity, and to discover solutions that are “fully human.”
* People are religious by nature even though their values are often corrupted by the disorder of sin.
Chapter 1 – The Dignity of the Human Person
Man as the Image of God
* Human beings are made in the image of God that they may exist in a loving relationship with Him and with each other.
* People abuse their freedom and bring about darkness and disorder through sin, harming their relationships with God and other people and becoming divided and incomplete within themselves.
The Essential Nature of Man
* Human beings are unities of body and immortal soul. The body is good even though it is wounded by sin and must be brought under the control of discipline.
* Designed to know and love God, all people have self-knowledge and freedom.
Dignity of the Intellect, of Truth, and of Wisdom
* Through their intellect, people discover the truth and actually share “in the light of the divine mind.”
* Wisdom allows people to know what is true and good, and there is a special need for wisdom in today's world.
Dignity of Moral Conscience
* Conscience helps human beings do good, avoid evil, and maintain their human dignity; it is a meeting place with God deep within the soul.
* There are objective moral truths that all people must adhere to.
The Excellence of Freedom
* Human beings have free will because they are created in the image of God. They must use that free will to choose what is good with the help of God's grace.
The Mystery of Death
* Because of Christ's victory, human beings, who have long been tormented by death, have hope for eternal life.
Kinds of Atheism and Its Causes
* Human dignity depends on communion with God, and full human life is only possible through relationship with God.
* Atheism, the rejection of God, is “one of the most serious problems of our time.” It arises from empiricism, relativism, extreme humanism, misunderstandings, apathy, misuse of modernity, and/or a “violent protest against the evil in the world.”
* Believers are sometimes partly at fault for the spread of atheism because they are careless about their religion and do not practice or present it faithfully.
* Atheism in today's world is often systematic, promoting human autonomy without dependence on God and claiming that “man is an end to himself.”
The Attitude of the Church Towards Atheism
* The Church rejects “harmful teachings and ways of acting” like atheism, which is “in conflict with reason and with common human experience” and deprives people of their dignity.
* True human dignity is always “grounded and brought to perfection in God.” People are made to be in relationship with Him, and only He can answer humanity's deepest questions.
* In order to combat atheism, Christians must present the truth faith in deed and word, love and unity. They must be witnesses to the truth in all situations. The Church, with the guidance of the Spirit, works to make God visible in the world even as she constantly seeks renewal and purification.
* The Christian message is “in harmony with the most secret desires of the human heart” and helps people attain true dignity, freedom, truth, and life.
Christ the New Man
* Christ Incarnate “fully reveals man to himself and brings to light his most high calling.” All truth has its source and perfect embodiment in Him.
* Human nature is restored through Christ, Who assumed it and raised it up to “a dignity beyond compare.”
* Through Christ, God reconciled humanity to Himself and opened the way to renewal, holiness, and meaning.
* Jesus is the only answer to the mystery of humanity.
The full text of Gaudium et Spes is available online at the Vatican website.