labour of one kind or another) into "productive" and
"unproductive" by the same authority (book ii. c. 3) is also apposite
both for purposes of political economy and practical guidance, though
economists have found it difficult to define where "productive
expenditure" ends and "unproductive expenditure" begins. Adam Smith
includes in his enumeration of the "fixed capital" of a country "the
acquired and useful abilities of all the inhabitants"; and in this sense
expenditure on education, arts and sciences might be deemed expenditure
of the most productive value, and yet be wanting in strict commercial
account of the profit and loss. It must be admitted that there is a
personal expenditure among all ranks of society, which, though not in
any sense a capital expenditure, may become capital and receive a
productive application, always to be preferred to the grossly
unproductive form, in the interest both of the possessors and of the
community.

The subject in its details is full of controversies, and a discussion
of it at any length would embrace the whole field of economics. The
subject will be found fully dealt with in every important economic
work, but the following may be specially consulted:--J.S. Mill,
_Principles of Political Economy_; J.E. Cairns, _Some Leading
Principles of Political Economy_; F.A. Walker, _Political Economy_; A.
Marshall, _Principles of Economics_; E. Bohm v. Bawerk, _Capital and
Interest_; K. Marx, _Capital_; J.B. Clark, _Capital and its Earnings_;
see also the economic works of W.H. Mallock (_Critical Examination of
Socialism_, 1908, &c.) for an insistence on the importance of
"ability," or brain-work, as against much of modern socialist
theorizing against "capitalism."

CAPITAL PUNISHMENT. By this term is now meant the infliction of the
penalty of death for crime under the sentence of some properly
constituted authority, as distinguished from killing the offender as a
matter of self-defence or private vengeance, or under the order of some
self-constituted or irregular tribunal unknown to the law, such as that
of the Vigilantes of California, or of lynch law (q.v.). In the early
stages of society a man-slayer was killed by the "avenger of blood" on
behalf of the family of the man killed, and not as representing the
authority of the state (Pollock and Maitland, _Hist. Eng. Law_, ii.
447.) This mode of dealing with homicide survives in the vendetta of
Corsica and of