It is true that, since society is composed of individuals, the nature and constitution of the units has to be considered in their mutual interaction, and therefore the study must have a biological basis: but when we have to consider the special action of the compound social environment upon the individual, the study is not one which can be properly considered from the purely biological side, nor is it to be comprised within the formula of individual life. With respect to the social environment Mr. Spencer says, "This additional factor in the problem of complete living, is, indeed, so important that the necessitated modifications of conduct have come to form a chief part of the code of conduct. Because the inherited desires, which directly refer to the maintenance of individual life, are fairly adjusted to the requirements, there has been no need to insist on that conformity to them which furthers self-conservation. Conversely, because these desires prompt activities that often conflict with the activities of others, and because the sentiments responding to other's claims are relatively weak, moral codes emphasise those restraints on conduct which the presence of fellow men entails. From the sociological point of view, then, Ethics becomes nothing else than a definite account of the forms of conduct that are fitted to the associated state, in such wise that the lives of each and all may be the greatest possible, alike in length and breadth. But here we are met by a fact which forbids us thus to put in the foreground the welfares of citizens, individually considered, and requires us to put in the foreground the welfare of the society as a whole. The life of the social organism must, as an end, rank above the lives of its units. These two ends are not harmonious at the outset, and though the tendency is towards harmonisation of them, they are still partially conflicting."[12] The difficulty alluded to arises from the fact that human society is not one well-ordered whole, but has been from the first, and still is, split up into numerous nations having conflicting interests: from which it follows that there is not a complete homogeneity of duty between man and man when, for instance, a state of warfare exists. If now we recognise Ethics as the rule of life imposed by Society upon the individual, we shall have to recognise great varieties of rule, according to the nature and objects of the particular Society imposing the rule, according to the state of development at which that Society has arrived, and according to the nature of the environment.