William Wistar Comfort

Stylianos Negrepontis

An ultrafilter is a truth-value assignment to the family of subsets of a set, and a method of convergence to infinity. From the first (logical) property arises its connection with two-valued logic and model theory; from the second (convergence) property arises its connection with topology and set theory. Both these descriptions of an ultrafilter are connected with compactness. The model-theoretic property finds its expression in the construction of the ultraproduct and the compactness type of theorem of Los (implying the compactness theorem of first-order logic); and the convergence property leads to the process of completion by the adjunction of an ideal element for every ultrafilter-i. e., to the Stone-Cech com- pactification process (implying the Tychonoff theorem on the compact- ness of products). Since these are two ways of describing the same mathematical object, it is reasonable to expect that a study of ultrafilters from these points of view will yield results and methods which can be fruitfully crossbred. This unifying aspect is indeed what we have attempted to emphasize in the present work.

The Theory of Ultrafilters

The Character Types in the Old French Chansons de Geste

The Moors in Spanish Popular Poetry Before 1600

Chrétien (de Troyes)

Erec et Enide

The 12th-century poet Chrétien de Troyes is chiefly responsible for the preservation of Arthurian myth and its eminent role in European literature. This sensitive translation of his verse narratives features four romances. Its tales of Lancelot and early Grail legends offer lively, accessible views of the ideals of French chivalry.

William Wistar Comfort

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