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Proceedings of the Bayed Society 
qiient criticism, all practical considerations — to distinguish doctrine 
from practice, to separate principle from precept, and construct 
science apart from art — is the first aim of the present inquiry. 
Precisely as biology underlies medicine, and astronomy navigation, 
so sound practical economics can only be profitably attempted after 
sound scientific conceptions have been attained. 
§ 3. The attainment of scientific princi]3les being aimed at, the 
scientific method, and the scientific method alone, must be used. 
This involves a further, a sterner, and a far more difficult assay of 
economic literature than the preceding, which aimed exclusively at 
the removal of irrelevant practical matter. The influence of other 
extra-scientific conceptions, theological or metaphysical,' optimistic 
or pessimistic, has also to be guarded against. 
§ 4. Having then successively eliminated as irrelevant to our 
present purpose the disturbing elements above referred to, what 
strictly scientific matter remains 1 Much ; yet this is in such a form 
as to demand a new analysis. For this, as in the preceding paper 
on statistics, two postulates are required — (1) the classification of tlie 
sciences, and (2) the main conceptions of each — the comparatively 
simple conceptions of physics preceding those of biology ; those of 
biology being followed by those of psychology, and these again by 
sociology. The elimination of practical and of philosophical considera- 
tions does not then suffice. Hew difficulties were in the first place 
shown * to depend not only upon the profound disagreement as to 
scope and method of the subject, but as to its very nature, some 
claiming it “ to be a logical science, others a mathematical, others a 
physical, others a biological, others a psychological, others a social, and 
others an ethical science ; while some hold it to belong partly to one 
of these sciences and partly to another.” Yet others, as if the wealth 
they are concerned with were not material, and the population of 
which they discuss the laws did not consist of living organisms, 
practically isolate it altogether from the sciences, even those of 
matter and life. The economist of literary or legal training assumes 
that subtle verbal definition expanded under the rules of formal 
logic will create a rigid, universal system. The mathematician up- 
holds the “ statistical method,” or the expression of economic laws 
by algebra and the calculus. But the economist of more practical 
* Classification of Statistics, p. 26. 
