for this short-sighted traffic of misguided human nature is enlightenment,--"instruction publique et privee des lois de l'ordre naturel."[6] The nature in terms of which all knowledge of phenomena--for the present purpose economic phenomena--is to be finally synthesised is, therefore, substantially of a quasi-spiritual or animistic character. The laws of nature are in the last resort teleological: they are of the nature of a propensity. The substantial fact in all the sequences of nature is the end to which the sequence naturally tends, not the brute fact of mechanical compulsion or causally effective forces. Economic theory is accordingly the theory (1) of how the efficient causes of the _ordre naturel_ work in an orderly unfolding sequence, guided by the underlying natural laws--the propensity immanent in nature to establish the highest well-being of mankind, and (2) of the conditions imposed upon human conduct by these natural laws in order to reach the ordained goal of supreme human welfare. The conditions so imposed on human conduct are as definitive as the laws and the order by force of which they are imposed; and the theoretical conclusions reached, when these laws and this order are known, are therefore expressions of absolute economic truth. Such conclusions are an expression of reality, but not necessarily of fact. Now, the objective end of this propensity that determines the course of nature is human well-being. But economic speculation has to do with the workings of nature only so far as regards the _ordre physique_. And the laws of nature in the _ordre physique_, working through mechanical sequence, can only work out the physical well-being of man, not necessarily the spiritual. This propensity to the physical well-being of man is therefore the law of nature to which economic science must bring its generalisations, and this law of physical beneficence is the substantial ground of economic truth. Wanting this, all our speculations are vain; but having its authentication they are definitive. The great, typical function, to which all the other functioning of nature is incidental if not subsidiary, is accordingly that of the alimentation, nutrition of mankind. In so far, and only in so far as the physical processes contribute to human sustenance and fullness of life, can they, therefore, further the great work of nature. Whatever processes contribute to human sustenance by adding to the material available for human assimilation and nutrition, by increasing the substance disposable for human comfort, therefore count towards the substantial end. All other processes, however serviceable in other than this physiological respect, lack the substance of economic reality. Accordingly, human industry is productive, economically speaking, if it heightens the effectiveness of the natural processes out of which the material of human sustenance emerges; otherwise not. The test of productivity, of