SUMMARY: This study proceeds in the context of the first part of the Constitution (GS 11-45), taking into account the introductionary exposition, in which the Council considers the condition of man, namely his hopes and anxieties, the profound changes actually existing in the world and the most common aspirations of humanity (GS 4-10). From the point of view of the christocentrism, proper to Gaudium et Spes, which indicates Christ as the Beginning and the End, certain themes concerning the dignity of the human person and the sense of man's activity in the created world are tackled in distinct paragraphs. As the centre of the cosmos and of history, Christ is the new Adam, the heir of the promises, the new man, he in whom and from whom acquire significance man and creation itself. Within the mystery of Christ, the image of the invisible God and the first-born of every creature, is realised the truth concerning man, created, in his twofold aspect of body and soul, to the image of the Word Incarnate. This truth on Christ and on man is essential both to christology and to biblical anthropology. In the context of the Creator's project and from the point of view of salvation history, the problem relative to the value of human activity is discussed. According to Gaudium et Spes, man is the agent of God in the universe. As his mandatory, he is destined to preserve and safeguard his dominion on the earth within the human and extrahuman sphere, and exercises this mandate in a priestly, prophetical and regal way. As collaborator of God, man is called to make a definite contribution to the worldsetting in which God has placed him.