It is true then that all the great fields of Greek literature make their several contributions to the material of our subject. And besides the works of the great masters, the student has to reckon with the secondary and parasitic work of the later scholiasts, compilers and commentators, which is even more replete with the special information upon which the history of Greek religion can be built. The study of it is, in fact, almost coextensive with the whole study of Greek literature. But amidst this profusion of material we must specially mark the works of those ancients who wrote direct treatises on the various religious phenomena, on the Gods, the cult-practices, the theologic and mythologic systems of the Hellenic societies. The earliest of such works that have come down to us are the poems of Hesiod and the Hesiodic school, the Works and Days and the Theogony, while of parts of the ‘Homeric’ hymns the special theme is the attributes and functions of the various divinities. But it was not till the period of scientific activity after Aristotle that definite treatises in prose on different departments of the national religion began to be rife. A chapter on sacrifice by Theophrastos is mainly preserved for us by Porphyry. The writers of ‘Atthides’ or Attic history and antiquities, who belonged mainly to the third century, were special workers in this field; Philochoros, the chief of them, wrote ‘on festivals,’ ‘on sacred days,’ ‘on divination,’ ‘on the Attic mysteries’; Istros, the slave and friend of Kallimachos, on the ‘manifestations of Apollo’ and on {11} ‘the Cretan sacrifices’; while the ‘exegetic work’ of Kleidemos was, if we may judge from the fragments that remain, occupied with the problems of religion and mythology. Outside this circle we hear of other contributions to the history of Greek religion, such as the treatises of Herakleides, probably the pupil of Aristotle, usually called ‘Pontikos,’ on ‘the foundations of temples,’ and ‘on oracles’; and a work by an unknown Sokrates of Kos on the important subject of ‘Invocation-titles of the Gods.’ Lastly may be mentioned here a treatise of Apollodoros, ‘περι Θεῶν,’ which, if he is to be identified with the author of the ‘Bibliotheca,’ was probably a learned account of the popular religion rather than a metaphysical enquiry.