The problem of the relation of universal conceptions to particular experiences had become a central one to the Greeks after Socrates. (See summary, p. 103.) It was natural that the same problem should arise with the new mediæval man and should delight him as an enigmatical question. But conditions were less favorable for the mediæval scholastic than for the Greek. The mediæval had scanty literary materials, no opportunity of testing his discussions by empirical observations, and his mind was untrained. In the Early Period scholasticism had the character of a mental game in logic. It consisted, on the whole, in the subtle spinning out of logical questions with the few fragments of Aristotle as a guide. This was dangerous to faith, but the church could not prevent it, for it was the only mental diversion open to monks of the schools of Charlemagne. The arguments often reveal great mental acuteness, although they have the appearance of triviality. The schools of the ninth century were given over to barren formalism, and this threatened to submerge the vigorous movement inaugurated by Erigena. “Can a prostitute become a virgin again through divine omnipotence?” “Does a mouse that eats the sacrament eat the body of God?” “How many angels can stand on the point of a needle?” These are examples of the prevailing verbal gymnastics of that time, and such problems can be found even in the works of Peter Lombard, Thomas Aquinas, and Duns Scotus. Logically stated the problem is that of the relation of particulars to universals. It is usually called the problem of the reality of general ideas. The question was started by a passage in that universally used text-book of the time――the _Isagoge_ of Porphyry, which was an introduction to Aristotle’s _Categories_. (See p. 102.) Porphyry divides the problem into three parts: (1) Do genera and species exist in nature, or do they exist as mere products of the intellect? (2) If they are things apart from the mind, are they corporeal or incorporeal things? (3) Do they exist outside the individual things of sense, or are they realized in the latter? Upon the problem involved here the thinkers of the Middle Ages were divided into three schools,――realists, conceptualists, and nominalists.[57] The realist maintained that the general idea had reality, while the particular was only a defective imitation of it. The nominalist, on the contrary, held that the universal is only a name (_nomen_) or an abstraction derived from the real particular thing. The conceptualist tried to mediate between the two by showing that reality exists only in the particular. To use the mediæval phrases, realism is _universalia ante rem_; nominalism is _universalia post rem_; conceptualism is _universalia in re_. (See p. 103 for table of comparison with Protagoras, Plato, and Aristotle.) The question was of great practical importance to the church. Is the universal church real and therefore all its dogma authoritative, or are