(1) God, pure actuality and absolute perfection, is substantially distinct from every finite thing: He alone can create and preserve all beings other than Himself. His infinite knowledge includes all that has been, is, or shall be, and likewise all that is possible.
(2) As to our knowledge of the material world: whatever exists is itself, an incommunicable, individual substance. To the core of self-sustaining reality, in the oak-tree for instance, other realities (accidents) are added -- size, form, roughness, and so on. All oak-trees are alike, indeed are identical in respect of certain constituent elements. Considering this likeness and even identity, our human intelligence groups them into one species and again, in view of their common characteristics, it ranges various species under one genus. Such is the Aristotelean solution of the problem of universals. Each substance is in its nature fixed and determined; and nothing is farther from the spirit of Scholasticism than a theory of evolution.
But this statism requires as its complement a moderate dynamism, and this is supplied by the central concepts of act and potency. Whatsoever changes is, just for that reason, limited. The oak-tree passes through a process of growth, of becoming: whatever is actually in it now was potentially in it from the beginning. Its vital functions go on unceasingly (accidental change); but the tree itself will die, and out of its decayed trunk other substances will come forth (substantial change). The theory of matter and form is simply an interpretation of the substantial changes which bodies undergo. The union of matter and form constitutes the essence of concrete being, and this essence is endowed with existence. Throughout all change and becoming there runs a rhythm of finality; the activities of the countless substances of the universe converge towards an end which is known to God; finality involves optimism.
(3) Man, a compound of body (matter) and of soul (form), puts forth activities of a higher order -- knowledge and volition. Through his senses he perceives concrete objects, e.g. this oak; through his intellect he knows the abstract and universal (the oak). All our intellectual activity rests on sensory function; but through the active intellect (intellectus agens) an abstract representation of the sensible object is provided for the intellectus possibilis. Hence the characteristic of the idea, its non-materiality, and on this is based the principal argument for the spirituality and immortality of the soul. Here, too, is the foundation of logic and of the theory of knowledge, the justification of our judgments and syllogisms.
Upon knowledge follows the appetitive process, sensory or intellectual according to the sort of knowledge. The will (appetitus intellectualis) in certain conditions is free, and thanks to this liberty man is the master of his destiny. Like all other beings, we have an end to attain and we are morally obliged, though not compelled, to attain it.
Natural happiness would result from the full development of our powers of knowing and loving. We should find and possess God in this world since the corporeal world is the proper object of our intelligence. But above nature is the order of grace and our supernatural happiness will consist in the direct intuition of God, the beatific vision. Here philosophy ends and theology begins.
Neo-Scholasticism rejects some medieval theories of physics, celestial and terrestrial, e.g. the perfection and superiority of astral substance, the "incorruptibility" of the heavenly bodies, their external connexion with "motor spirits", the influence of the stars on the generation of earthly beings, the four "simple" bodies, etc. It further rejects those philosophical theories which are disproved by the results of investigation; e.g. the diffusion of sensible "species" throughout a medium and their introduction into the organs of sense. It follows the example of the Aristotelean and medieval philosophy in taking the data of research as the groundwork of its speculation. It is not possible to explain the world of phenomena while neglecting the phenomena that make up the world.
The medieval scholars cultivated the history of philosophy solely with a view to its utility, i.e. as a means of gathering the deposit of truth contained in the writings of the ancients and, especially, for the purpose of refuting error. Neo-Scholasticism employs critical methods; it does not attempt to condense the opinions of others into a syllogism and refute them with a phrase. Its chief concern is with present-day systems. It takes issue with them and offsets their theories of the world by a synthesis of its own. Neo-Scholasticism found itself face to face the systems in vogue, especially of Positivism and Criticism. And it had to take up, from its own point of view, the significance of such concepts as being, substance, absolute, cause, potency, and act. It further needed to show that God is not unknowable; to rebut the charges gainst the traditional proofs of God's existence; to deal with the materials furnished by ethnography and the history of religions; and to study the various forms which monism and immanentism assume.
Neo-Scholasticism gained among Catholics of the later nineteenth century, against other views such as Ontologism, Traditionalism, the dualism of Anton Günther, and the thought of Descartes. It was endorsed by four Catholic Congresses: Paris (1891); Brussels (1895); Freiburg (1897); Munich (1900).
In Italy, the movement was vigorous from the start. The Accademia di San Tommaso, founded in 1874, published up to 1891 a review entitled "La Scienza Italiana". Numerous works were produced by Giuseppe Pecci, Tommaso Maria Zigliara (1833-93), Satolli (1839-1909), Liberatore (1810-92), Barberis (1847-96), Schiffini (1841-1906), de Maria, Talamo, Lorenzelli, Ballerini, Matussi and others. The Italian writers at first laid special emphasis on the metaphysical features of Scholasticism, without paying sufficient attention to the sciences or to the history of philosophy. Later this underwent a change which promises excellent results.
From Italy the movement spread into the other European countries and found supporters in Germany such as Kleutgen, Stöckl, the authors of the "Philosophia Lacensis" published at Maria Laach by the Jesuits (Pesch, Hontheim, Cathrein), Gutberlet, Commer, Willmann, Kaufmann, Glossner, Grabmann and Schneid. These scholars have made valuable contributions to the history of philosophy, especially that of the Middle Ages. Stöckl led the way with his "Geschichte d. Philosophie des Mittelalters" (Mainz, 1864-66). Ehrle and Denifle founded in 1885 the "Archiv für Literatur u. Kirchengesch. d. Mittelalters", and the latter edited the monumental "Chartularium" of the University of Paris. In 1891, Von Hertling and Bäumker began the publication of their "Beiträge zur Gesch. d. Phil. des Mittelalters".
Belgium has been particularly favoured. Leo XIII established in 1891 at Louvain (then still a francophone university) the "Institut de philosophie" for the special purpose of teaching the doctrine of St. Thomas together with history and the natural sciences. The Institute was placed in charge of Mgr (later Cardinal) Mercier whose "Cours de philosophie" has been translated into the principal languages of Europe.
In France, besides those already mentioned, Vallet, Gardair, Fonsegrive and Piat have taken a prominent part in the movement; in the Netherlands (Amsterdam) de Groot; in Switzerland (Freiburg), Mandonnet; in Spain, Orti y Lara, Urráburu, Gómez Izquierdo; in Mexico, Garcia; in Brazil, Santroul; in Hungary, Kiss and Pecsi; in England, Clarke, Maher, John Rickaby, Joseph Rickaby, Boedder (Stonyhurst Series); in the United States, Coppens, Poland, Brother Chrysostom, and the professors at the Catholic University (Shanahan, Turner, and Pace). A considerable number of reviews have served as its exponents: "Divus Thomas" (1879- 1903); "Rivista Italiana di filosofia neo-scolastica" (Florence, since 1909); "Annales de Philosophie Chrétienne" (Paris, since 1830); "Revue néo-scolastique de Philosophie" (Louvain, since 1894); "Revue de Philosophie" (Paris, since 1900);" Revue des Sciences philosophiques et théologiques" (Kain, Belgium, since 1907); "Revue Thomiste" (Paris, since 1893); "Philosophisches Jahrbuch für Philosophie und spekulative Theologie" (Paderborn, since 1887); "St. Thomas Blätter" (Ratisbon, since 1888); Bölcseleti-Folyóirat (Budapest, since 1886);" Revista Lulliana" (Barcelona, since 1901); "Cienza Tomista" (Madrid, since 1910). In addition to these, various periodical publications not specially devoted to philosophy have given neo-Scholasticism warm attention.