lane's trans. of Ibn Khallik[=a]n's _Biographical
Dictionary_ (Paris and London, 1842), vol. iii. pp. 130 ff., and Ibn
'Usaibi'a's biography translated in P. de Gayangos' edition of the _History
of the Mohammedan Dynasties in Spain_, by al-Maqqari (London, 1840), vol.
ii., appendix, p. xii. List of extant works in C. Brockelmann's _Geschichte
der arabischen Litteratur_, vol. i. p. 460. For his philosophy cf. T. J. de
Boer's _The History of Philosophy in Isl[=a]m_ (London, 1903), ch. vi.

(G. W. T.)

AVENARIUS, RICHARD HEINRICH LUDWIG (1843-1896), German philosopher, was
born in Paris on the 19th of November 1843. His education, begun in Zuerich
and Berlin, was completed at the university of Leipzig, where he graduated
in 1876. In 1877 he became professor of philosophy in Zuerich, where he
died on the 18th of August 1896. At Leipzig he was one of the founders of
the _Akademisch-philosophische Verein_, and was the first editor of the
_Vierteljahrsschrift fuer wissenschaftliche Philosophie_. In 1868 he
published an essay on the Pantheism of Spinoza. His chief works are
_Philosophie als Denken der Welt gemaess dem Princip des kleinsten
Kraftmasses_ (1876) and the _Kritik der reinen Erfahrung_ (1888-1890). In
these works he made an attempt to co-ordinate thought and action. Like
Mach, he started from the principle of economy of thinking, and in the
_Kritik_ endeavoured to explain pure experience in relation to knowledge
and environment. He discovers that statements dependent upon environment
constitute pure experience. This philosophy, called Empirio-criticism, is
not, however, a realistic but an idealistic dualism, nor can it be called
materialism.

See Wundt, _Philos. Stud._ xiii. (1897); Carstanjen and Willy in _Zeitsch.
f. wiss. Philos_. xx. (1896), 361 ff.; xx. 57 ff.; xxii. 53 ff.; J.
Petzoldt's _Einfuehrung in d. Philos. d. reinen Erfahrung_ (1900).

AVENGER OF BLOOD, the person, usually the nearest kinsman of the murdered
man, whose duty it was to avenge his death by killing the murderer. In
primitive societies, before the evolution of settled government, or the
uprise of a systematized criminal law, crimes of violence were regarded as
injuries of a personal character to be punished by the sufferer or his
kinsfolk. This right of vengeance was common to most countries, and in many
was the subject of strict regulations and limitations. It was prevented
from running into excesses by the law of sanctuary (_q.v._) and i