Such is the connection between the _Meno_ and the _Phaedo_; the life that was before and the life that shall be hereafter depend upon the Ideal world. That salvation is in this life and in the practical sphere of human government is possible only through a knowledge of these Ideas is the doctrine of the immortal _Republic_. This great work in ten books is well known, but its unique value is not always recognised. It starts with a discussion of Justice. Thrasymachus, a brazen fellow like Callicles in the _Gorgias_, argues that Justice is the interest of the stronger and that law and morality are mere conventions. The implications of this doctrine are of supreme importance. If Justice is frank despotism, then the Eastern type of civilisation is the best, wherein custom has once for all fixed the right of the despot to grind down the population, while the sole duty of the latter is to pay taxes. The moral reformation of law becomes impossible; no adjustment of an unchanging decree to the changing and advancing standard of public morality can be contemplated; constitutional development, legal reformation and the great process by which Western peoples have tried gradually to make positive law correspond with Ethical ideals are mere dreams. But the verbal refutation of Thrasymachus does not satisfy Glaucus and Adeimantus who are among Socrates' audience. In order to explain the real nature of Justice, Socrates is compelled to trace from the very beginning the process by which states have come into existence. Economic and military needs are thoroughly discussed. The State cannot continue unless there is created in it a class whose sole business it is to govern. This class is to be produced by communistic methods; the best men and women are to be tested and chosen as parents, their children being taken and carefully trained apart for their high office. This training will be administered to the three component parts of the soul, the rational, the spirited and the appetitive, while the educational curriculum will be divided into two sections, Gymnastic for the body and Artistic for the mind--the latter including all scientific, mathematical and literary subjects. After a careful search, in this ideal state Justice, the principle of harmony which keeps all classes of the community coherent, will show itself in "doing one's own business".