it were, of philosophy; it is, to use an Aristotelian phrase, potential philosophy. Philosophy, in turn, is science in actu, the most exalted function of the scholar, the supreme satisfaction of the scientific spirit and its natural tendency to comprehend everything into a unity.

Philosophy and science are intimately related, not only in essence and in interests, but also as to their origin and destiny. Animated by the same all-powerful instinct to discern the causes of things rerum cognoscere causas · and to comprehend them into the unity of a first cause, the human mind no sooner reaches certain elementary truths in physics, mathematics, and morals, than it hastens to synthesize them, to form them into universal theories, into ontological and cosmological systems, i. e. to philoso phize, to make metaphysics. It makes up for its ignorance of reality either by means of the imagination, or by that wonderful instinct of childhood and of genius which divines the truth without searching for it. This accounts for the aprioristic, idealistic, and fantastic character of the philosophy of the ancients, as well as for its incomparable grandeur. In proportion as our stock of positive knowledge is increased, as scientific labor is divided and consequently developed, philosophy becomes more and more differentiated from poetry; its methods are recognized, its theories gain in depth what the sciences acquire in scope. Every scientific movement gives rise to a philosophical movement; every new philosophy is a stimulus to science.? Though this bondri of union seems to have been ruptured during the Middle Ages, the breach is but an apparent one. Whatever hostility or indifference is manifested towards science, comes from the official philosophy of the School; it is never found among the independent philosophers, be they Christians, Jews, or Arabians. There may be as much opposition between science and a certain philosophy in the nineteenth century as there was in the times of Roger Bacon and Lord Verulam

True science and true philosophy have always been in perfect accord, and though there may be a semblance of rivalry, their relations are to-day as harmonious as they can be.1

§ 2. Division

To the Ionian Greeks belongs the honor of having crea ted2 European philosophy; to the Neo-Latins and the Ger mans, that of having given to it its modern development.

Hence there are, in the history to be outlined by us, two great and wholly distinct epochs, which are connected by the Middle Ages (period of transition).

1 [On the nature and import of philosophy, and its relation to other sciences, consult Ladd, Introduction to Philosophy, New York, 1891; Volkelt, Vorträge zur Einführung in die Philosophie der Gegen wart, Munich, 1892; Paulsen, Einleitung in die Philosophie, 3d ed. Berlin, 1895; English translation by Frank Thilly, New York, 1895, -TR.]

2 By this word we do not mean to imply the absolute originality of Hellenic philosophy. The influence exercised upon its development by the Orient cannot be doubted. There is no trace of philosophy, properly so called, among the Greeks before they come in contact with Egypt, that is, before the reign of Psammetichus, who admits them into the country. Moreover, the fathers of Greek philosophy are all Ionians; from Asia Minor philosophy was imported, first into Italy, and at a comparatively recent period into Athens, that is, into Greece proper. But what is most important, we find in Ionian phil osophy, and that too at its very outset, conceptions the boldness of which is in marked contrast with the comparative timidity of Attic philosophy, conceptions which pre-suppose a long line of intellectual development. The influence of Egyptian and Chaldean science, which is, moreover, attested by Herodotus, may be compared to that exer cised by the Arabian schools upon the development of Christian thought in the Middle Ages. It has been exaggerated by Röth (Ge schichte unserer abendländischen Philosophie, vol. I., 1846, 1862; vol. II., 1858) and unjustly denied by Zeller (Die Philosophie der Griechen, 5th ed. 1892, vol. I.; English translation by Sarah Alleyne). Concerning the relation of Pythagoreanism and Platonism to Indian and Iranian speculation, and the part played by Babylon as the centre of intellec tual exchange between the Orient and the Occident, see § 9.

I. In the development of Greek philosophy, we have two separate periods,-a period of spontaneous creation, and one of sceptical reflection and reproduction.

1. The problem which dominates the former is the problem of the origin of things: the problem of becoming. Among the Ionians, this philosophy assumes the form of materialistic pantheism; among the Italian philosophers, who are influenced by the Doric spirit, it is essentially spiritualistic pantheism. The systems produced by these two schools contain in germ all the doctrines of the future, especially the monistic and atomistic hypotheses, the two poles of modern scientific speculation. - From Thales to Protagoras, or from 600 to 440 B. C.

2. The age of critical reflection is inaugurated by the πάντων μέτρον ἄνθρωπος of the Sophists. This period evolves the important truth, foreshadowed by Zeno, Par menides, and Anaxagoras, that the human understanding is a coefficient in the production of the phenomenon. To the problems of nature are added the problems of the soul, to the cosmological questions, logical and critical questions; to the speculations on the essence of things, investigations concerning the criterion of truth and the end of life. Greek philosophy reaches its highest development in Plato, as far as depth is concerned; in Aristotle and in the science of Alexandria, as regards analysis and the extent of its inquiries.

II. Scientific progress, and consequently speculation, was arrested by the invasion of the Northern races. The philosophical spirit was extinguished for want of something to nourish it. Ten centuries of uninterrupted labor were followed by ten centuries of sleep, a sleep that was deep at first, and then broken by bright dreams of the past (Plato and Aristotle) and forecasts of the future. Although the logic of history is less transparent during the middle ages than before and after this period of transition, we

notice two epochs that run parallel with those of Attic philosophy: one, Platonic, realistic, turned towards the past (from St. Augustine to St. Anselm), the other, Peripatetic, nominalistic, big with the future.

III. Modern philosophy dates from the scientific and literary revival in the fifteenth century. Its history, like that of Greek speculation, presents, —

1. A period of expansion and ontological synthesis (Bruno, Descartes, Spinoza, Leibniz), and,

2. A period of critical reflection and analysis (essays concerning the human understanding: Locke, Hume, Kant, and his successors).

§ 3. Sources

The principal sources for the history of philosophy are: For pre-Socratic speculation: Plato and Aristotle.1 For Socrates: Xenophon2 and Plato, particularly the Apology, the Crito, and the Phædo.

For Plato: the Republic, the Timæus, the Symposium, the Phædrus, the Theatetus, the Gorgias, the Protagoras.3

For Aristotle: the Metaphysics, the Logic, the Ethics, the Physics, the Psychology, the Politics; the commentators of Aristotle, especially Simplicius.*

1 Especially the first book of the Metaphysics (see § 17, first note), which is a historical summary of philosophy from Thales to Aristotle. The fragments of the pre-Socratic authors have been collected by Mullach, Fragmenta phil. græc. ante Socratem, 3 vols., Paris, 1860 [also by Ritter and Preller (mentioned on page 8). English translations in Burnet's Early Greek Philosophy (page 8), and of Heraclitus, in Patrick's Heraclitus on Nature. For translations of classical writers, consult Bohn's Classical Library. TR.].

2 Memorabilia Socratis recens. J. G. Schneider, Oxf., 1813.

8 [See § 16, note 2. - TR.]

Comment. in Arist. physicorum libros, ed. by Hermann Diels, Berlin, 1882; Comment. in libros de anima, ed. by M. Hayduck, Berlin, 1882.

For the post-Aristotelian schools and Greek philosophy in general: Lucretius,1 Cicero,2 Seneca,3 Plutarch, Sextus Empiricus, Diogenes Laertius,6 Clement of Alexandria,7 Origen, Hippolytus, Eusebius,10 Plotinus,11 Porphyry,"1

1 Lucretii Cari de rerum natura libb. C. Lachmann rec. et illustr., Berlin, 1850 ff. [edited also by Bernays, Munro, and others].

2 The De divinatione et de fato, the De natura deorum, the De officiis, the De finibus, the Tusculance disputationes, and the Academica; Opera omnia, ed. Le Clerc, Bouillet, Lemaire, 17 vols., Paris, 1827-32; Opera philosophica, ed. Goerenz, 3 vols., Leipsic, 1809-1813; Ciceronis historia philosophic antiquæ, ex omnibus illius scriptis collegit F. Gedike, Berlin, 1782, 1801, 1814.

* Opera quæ extant c. not. et comment. varior., 3 vols., Amsterdam, 1672.

De physicis philosophorum decretis libb., ed. Beck, Leipsic, 1777; Scripta moralia, 6 vols., Leipsic, 1820; Opera omnia graece et latine ed. Reiske, 12 vols., Leipsic, 1774-82.

Sexti Empirici opera (Пvpówveiwv vπотvπwσewv libb. III.; Adversus mathematicos libb. XI.) græc. et lat. ed. Fabricius, Leipsic, 1718 and 1812; ed. Emm. Bekker, Berlin, 1812.

6 Diogenis Laertii de vitis, dogmatibus et apophthegmatibus clarorum philosophorum libb. X. græce et latine ed. Hübner, 2 vols., Leipsic, 1828, 1831; D. L. 1. X. ex Italicis codicibus nunc primum excussis recensuit C. Gabr. Cobet, Paris, 1850. Diogenes Laertius flourished about 230 of our era.

7 Clementis Alexandrini opera, Leipsic, 1830-34 (Aóуos пρotρettikòs πρὸς Ἕλληνας; Παιδαγωγός; Στρωματεῖς).

De principiis gr. ed. c. interpret. lat. Rufini, et annot. instruxit ed. R. Redepenning, Leipsic, 1836; Contra Celsum libb. ed. Spencer, Cambridge, 1671; Origenis opera omnia quæ græce vel latine tantum exstant et ejus nomine circumferuntur, ed. C. et C. V. Delarue, denuo recens. emend. castig. C. H. E. Lommatzsch, 25 vols., Berlin, 1831-48.

S. Hippolyti refutationis omnium hæresium libror. X. quæ supersunt græce et latine ed. Duncker et Schneidewin, Gött. 1856-59. The first book, known by the title poropovμeva, was for a long time attributed to Origen; books IV.-X., which were discovered in Greece in 1842, were first published by Emm. Miller, Oxford, 1851, under the title Origenis philosophumena, etc.

10 Eusebii Pamph. Præparatio evangelica ed. Heinichen, Leipsic 1842.

11 See $ 25.