APRIL  , the second

month of the ancient Roman, and the fourth of the modern calendar, containing thirty days . The derivation of the name is uncertain . The traditional etymology from Lat. aperire, " to open," in allusion to its being the season when trees and flowers begin to " open," is supported by comparison with the modern Greek use of avocEis (opening) for spring . This seems very possible, though, as all the Roman months were named, in honour of divinities, and as April was sacred to Venus, the Festum Veneris et Fortunae Virilis being held on the first day, it has been suggested that Aprilis was originally her month Aphrilis, from her Greek name Aphrodite . Jacob Grimm suggests the name of a hypothetical god or hero, Aper or Aprus . On the fourth and the five following days, games (Ludi !Llegalenses) were celebrated in honour of Cybele; on the fifth there was the Festum Fortunae Publicae; on the tenth (?) games in the circus, and on the nineteenth equestrian combats, in honour of Ceres; on the twenty-first—which was regarded as the birthday of Rome—the Vinalia urbana, when the wine of the previous autumn was first tasted; on the twenty-fifth, the Robigalia, for the averting of mildew; and on the twenty-eighth and four following days, the riotous Floralia . The Anglo-Saxons called April Oster-monath or Eostur-monath, the period sacred to Eostre or Ostara, the pagan Saxon goddess of spring, from whose name is derived the modern Easter . St George's day is the twenty-third of the month; and St Mark's Eve,' with its superstition that the ghosts of those who are doomed to die within the year will be seen to pass into the church, falls on the twenty-fourth . In China the symbolical ploughing of the earth by the emperor and princes of the blood takes place in their third month, which frequently corresponds to our April; and in Japan the feast of Dolls is celebrated in the same month . The " days of April " (journees d'avril) is a name appropriated in French history to a series of insurrections at Lyons, Paris and elsewhere, against the government of Louis Philippe in 1834, which led to violent repressive measures, and to a famous trial known as the proces d'avril . See Chambers's Book of Days; Grimm's Geschichte der deutschen Sprache, Cap . " Monate"; also APRIL-FooLs' DAY .

APRIL-FOOLS' DAY, or ALL-FooLS' DAY, the name given to the 1st of April in allusion to the

custom of playing practical jokes on friends and neighbours on that day, or sending them on fools' errands . The origin of this custom has been much disputed, and many ludicrous solutions have been suggested, e.g. that it is a farcical commemoration of Christ being sent from Annas to Caiaphas, from Caiaphas to Pilate, from Pilate to Herod, and from Herod back again to Pilate, the crucifixion having taken place about the 1st of April . What seems certain is that it is in some way or other a relic of those once universal festivities held at the vernal equinox, which, beginning on old New Year's day, the 25th of March, ended on the 1st of April . This view gains support from the fact that the exact counterpart of April-fooling is found to have been an immemorial custom in India . The festival of the spring equinox is there termed the feast of Huli, the last day of which is the 31st of March, upon which the chief amusement is the befooling of people by sending them on fruitless errands . It has been plausibly suggested that Europe derived its April-fooling from the French . They were the first nation to adopt the reformed calendar, Charles IX. in 1564 decreeing that the year should begin with the 1st of January . Thus the New Year's gifts and visits of felicitation which had been the feature of the 1st of April became associated with the first day of January, and those who disliked the change were fair butts for those wits who amused themselves by sending mock presents and paying calls of pretended ceremony on the 1st of April . Though the 1st of April appears to have been anciently observed in Great Britain as a general festival, it was apparently not until the beginning of the 18th century that the making of April-fools was a common custom . In Scotland the custom was known as " hunting the gowk," i.e. the cuckoo, and April-fools were " April-gowks," the cuckoo being there, as it is in most lands, a term of contempt . In France the person befouled is known as Poisson d'avril . This has been explained from the association of ideas arising from the fact that in April the sun quits the zodiacal sign of the fish .

A far more natural explanation would seem to be that the April fish would be a

young fish and therefore easily caught . A PRIORI (Lat. a, from, prior, Arius, that which is before, precedes), (I) a phrase used popularly of a judgment based on general considerations in the absence of particular evidence; (2) a logical term first used, apparently, by Albert of Saxony (14th century), though the theory which it denotes is as old as Aristotle . In the order of human knowledge the particular facts of experience come first and are the basis of generalized laws or causes (the Scholastic notiora nobis); but in the order of nature the latter rank first as the self-existent, fundamental truths of existence (notiora naturae) . Thus to Aristotle the a priori argument is from law or cause to effect, as opposed to what we call a posteriori (posterior, subsequent, derived), from effect to cause . Since Kant the two phrases have become purely adjectival (instead of adverbial) with a technical controversial sense, closely allied to the Aristotelian, in relation to knowledge and judgments generally . A priori is applied to judgments which are regarded as independent of experience, and belonging to the essence of thought; a posteriori to those which are derived from particular observations . The distinction is analogous to that between analysis and synthesis, deduction and induction (but there may be a synthesis of a priori judgments, cf . Kant's " Synthetic Judgment a priori ") . Round this distinction a rather barren controversy has raged, and almost all modern philosophers have labelled themselves either " Intuitionalist " (a priori) or " Empiricist " (a posteriori) according to the view they take of knowledge . In fact, however, the rival schools are generally arguing at cross purposes; there is a knowledge based on particulars, and also a knowledge of laws or causes . But the two work in different spheres, and are complementary . The observation of isolated particulars gives not necessity, but merely strong probability; necessity is purely intellectual or " transcendental." If the empiricist denies the intellectual element in scientific knowledge, he must not claim absolute validity for his conclusions; but he may hold against the intuitionalist that absolute laws are impossible to the human intellect .

On the other

hand, pure a priori knowledge can be nothing more than form without content (e.g. formal logic, the laws of thought) . The simple fact at the bottom of the controversy is that in all empirical knowledge there is an intellectual element, without which there is no correlation of empirical data, and every judgment, however simple, postulates a correlation of some sort if only that between the predicate and its contradictory .