The purpose of the investigation is to determine the contribution of Jaime Balmes (1810-1848) to Roman Catholic thought during the first half of the nineteenth century, and his particular contribution to Spanish Catholicism. Balmes must be seen in the light of the revival of Roman Catholicism which took place throughout Europe during the Napoleonic and Restoration periods, manifested in the nostalgic return to religion, the restoration of worship, and the growth of the influence of the papacy. During this same period, however, anticlericalism, and religious conflict continued throughout Europe, particularly in Spain, where there were few signs of a religious restoration until 1839. New schools of Roman Catholic apologetics arose, which were characterized by a realistic approach to the problems of religious knowledge, Church and State, and religion and society. The new apologetics were popular in Spain in the early nineteenth century. After 1840, chiefly through Balmes, Spain played a more creative role in the revival of apologetics. Balmes' political thought contains elements of French and Spanish traditionalism, scholasticism, and moderate Liberal Catholicism. His political ideal was a strongly Catholic, paternalistic monarchy; but he accepted inevitable political and social change, advocating the use of democratic liberties in the defense of the Church. He achieved no synthesis of conservative and liberal political ideals, but adopted a conciliatory attitude toward the Spanish factions. He gave Spaniards a broad historical and philosophical understanding of their religious struggles, and awakened them to the social implications of religion. Balmes' chief contribution to apologetics was a popular work devoted to the social importance of religion in European history. This work, known throughout Europe, was written in imitation of the French social apologetics, sharing their theological superficiality, but surpassing them in orthodoxy and thoroughness of development. Balmes' philosophical works were likewise read throughout Europe, for they provided a sounder basis for Roman Catholic aoologetics than most Roman Catholic philosophies of the period, which tended toward heterodoxy. Balmes failed in his attempt to build a broader foundation for philosophical certitude than that of the eighteenth century rationalists; but his criterion of "common sense" provided a useful philosophical basis for religious dogmatism. He combatted the scepticism inherent in extreme sensationalism and subjective idealism, upholding the Scholastic balance between sense-perception and intellectual activity as factors in cognition. He combatted the Kantian tendency toward subjectivism, and upheld the objective validity of our knowledge of the real world. His philosophy was eclectic. Its chief weakness was a lack of unity and integration. Balmes revived and popularized many elements of scholastic philosophy, and may be regarded as the earliest precursor of the neo-scholastic movement of the late nineteenth century. In many respects, Balmes' thought typifies that of the Roman Catholic Revival. It had a broad general scope and effectively demonstrated the wider social and philosophical implications of religion; but it lacked a strong religious emphasis. Balmes did much to accommodate modern thought to the doctrine of the Roman Church; but like virtually all orthodox Roman Catholic apologists of his time, he achieved little in the way of creative synthesis, whether in politics or philosophy. Nevertheless, he made a unique contribution to Spanish Catholicism. He was the soul of the Catholic resistance to the anti-religious spirit of the age. He awoke Spain to its need for coming to terms with European civilization; and without abandoning the Spanish scholastic tradition, he enriched Spanish aoologetics through contact with European thought.