If the discussion of the nature and formation of character be regarded as the central topic of the _Ethics_, the contents of Book I., cc. iv.-xii. may be considered as still belonging to the introduction and setting, but these chapters contain matter of profound importance and have exercised an enormous influence upon subsequent thought. They lay down a principle which governs all Greek thought about human life, viz. that it is only intelligible when viewed as directed towards some end or good. This is the Greek way of expressing that all human life involves an ideal element—something which it is not yet and which under certain conditions it is to be. In that sense Greek Moral Philosophy is essentially idealistic. Further it is always assumed that all human practical activity is directed or “oriented” to a _single_ end, and that that end is knowable or definable in advance of its realisation. To know it is not merely a matter of speculative interest, it is of the highest practical moment for only in the light of it can life be duly guided, and particularly only so can the state be properly organised and administered. This explains the stress laid throughout by Greek Moral Philosophy upon the necessity of knowledge as a condition of the best life. This knowledge is not, though it includes knowledge of the nature of man and his circumstances, it is knowledge of what is best—of man’s supreme end or good. But this end is not conceived as presented to him by a superior power nor even as something which _ought_ to be. The presentation of the Moral Ideal as Duty is almost absent. From the outset it is identified with the object of desire, of what we not merely judge desirable but actually do desire, or that which would, if realised, satisfy human desire. In fact it is what we all, wise and simple, agree in naming “Happiness” (Welfare or Well-being)