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, prius_, that which is before, precedes),
(1) 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 tha