167 We who, in spite of Our inadequacy, are nevertheless the vicar of Him whom the prophet announced as the Prince of Peace, (70) conceive of it as Our duty to devote all Our thoughts and care and energy to further this common good of all mankind. Yet peace is but an empty word, if it does not rest upon that order which Our hope prevailed upon Us to set forth in outline in this encyclical. It is an order that is founded on truth, built up on justice, nurtured and animated by charity, and brought into effect under the auspices of freedom.
Source: Pacem in Terris (Vatican.va)