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subsequent construction of systematic economics can be obtained and 
tested; and to point out the road which may lead to the elucidation 
of such principles — without any pretence at exhaustive treatment of 
detail — is the aim of this paper. The existing economic literature, 
then, will henceforth be regarded as a storehouse of ideas of all 
kinds and ages, which, in so far as scientific, we have to disentangle 
and arrange on the plan above outlined into bodies of principles, 
dealing with each successive aspect of the subject, physical, biolo- 
gical, psychological, and social, these forming separate chapters, 
each accompanied by a summary, while the appreciation of the 
history of economics will be postponed. The inquiry as to the 
logical method or grammar of economics, and the mathematical 
principles involved in its treatment, instead of forming the subject 
of an initial dissertation, will be relegated to a final appendix also 
of partially historical character. 
§ 10. But the economist, even if not refusing the systematic 
application of science above proposed, will urge that economics 
must not only be pure but applied, not only scientific but practical. 
Assuredly so ; for while eliminating as irrelevant any admixture of 
practical considerations with the purely scientific portion of the 
subject, it will yet be attempted, in an appendix to each chapter, 
though of course only in the most brief and general way, to indicate 
the possible lines of modification of each set of factors, whether such 
modification has been effected or attempted in past or present time, 
proposed by any of the various schools of practical economists, or 
suggested by scientific knowledge. 
§ 11. The plan proposed is thus easily applicable to the wants of 
either specialist or generaliser, whether of scientific or practical 
bias ; for the chapters may thus be successively read for the doc- 
trine, and their respective appendices thereafter for the derived 
practice. And when the work is completed, while those especially 
familiar with the preliminary sciences will doubtless prefer the 
ascending order from physics onwards, the student whose interests 
lie rather in the supreme social and practical aspects of the subject, 
will without much inconvenience take the chapters and appendices 
in the reverse or descending order. 
§ 12. But even then we have no system of economics. True, 
nor has any system yet existed, the innumerable so-called systems 
