23 The worship rendered by the Church to God must be, in its entirety, interior as well as exterior. It is exterior because the nature of man as a composite of body and soul requires it to be so. Likewise, because divine Providence has disposed that "while we recognize God visibly, we may be drawn by Him to love of things unseen." Every impulse of the human heart, besides, expresses itself naturally through the senses; and the worship of God, being the concern not merely of individuals but of the whole community of mankind, must therefore be social as well. This obviously it cannot be unless religious activity is also organized and manifested outwardly. Exterior worship, finally, reveals and emphasizes the unity of the mystical Body, feeds new fuel to its holy zeal, fortifies its energy, intensifies its action day by day: "for although the ceremonies themselves can claim no perfection or sanctity in their won right, they are, nevertheless, the outward acts of religion, designed to rouse the heart, like signals of a sort, to veneration of the sacred realities, and to raise the mind to meditation on the supernatural. They serve to foster piety, to kindle the flame of charity, to increase our faith and deepen our devotion. They provide instruction for simple folk, decoration for divine worship, continuity of religious practice. They make it possible to tell genuine Christians from their false or heretical counterparts."
Source: Mediator Dei (Vatican.va)