220 HARVARD LAW REVIEW. mitting no third supposition ; but it falls to the ground with the failure of the prior and main division. There is no scientific ad- vantage to be attained in accurately dividing a mere heterogeneous mass. The futility of such an attempt is precisely exemplified in the following example, which I beHeve to be an accurate analogue to the suggested scheme of the learned author : Animals may be divided into those which are human and all other animals, and the latter may be again divided into those that are white and those that are colored. In this illustration it will be readily seen that if the class "all other animals" were a true genus, as, for example, the genus bear, white might readily become the true and scientifi- cally valuable mark of a species, as, for example, the white or polar bear, but that as it is, by reason of the insufficiency of the prior division, it has lost any such possible value. So it is with the distinction between positive and negative obligations. It is a dis- tinction which is applied to a class containing, for aught that appears to the contrary, many subdivisions and which may there- fore override the lines of subdivision. It may therefore on the one hand group many obligations which on closer inspection would be seen to be quite different and separately classifiable, and on the other may divide obligations which should not be divided. Assuming, however, that the subdivision into obligations to for- bear and obligations to act is possible of interpretation as a division along lines of inherent likeness, I yet incline strongly to the opinion that the class of obhgations to act is after all in the learned author's essential meaning not to be so interpreted, but is on the contrary, merely exclusionary. It is to be remembered that he was already furnished with the historical conception of torts as a class by themselves in which the duty was to forbear, and that conception was apparently his starting point. A mere exclusionary process would therefore give him his second class of obligations, obliga- tions to act. Moreover an examination of the obligations which he includes within its limits discloses such a diversity of character as would inevitably suggest further classification, if his object had been to find elements of likeness. Finally his constant use of the process of exclusion as a method of argument lends probative force to the idea that it was his method of classification as well. If this be the correct interpretation of the learned author's theory, as I believe it is, it follows that this suggested method of classification does not differ in any material aspect from that which I had my- self deduced from his arguments respecting individual obligations,
