There is an indefinite number of particular political questions that can arise, and many of them have their theoretical side. There is, therefore, no end to the possible additions that could be made to a treatise such as this. But ‘economic considerations’ means something wider than the special studies of professional economists, and there is room for a brief examination of some of the things that the phrase may suggest. People may, for instance, feel the need of the services of ministers of religion, and may be ready to pay for them. There may also be a good deal of organisation involved in meeting people’s religious needs. Human behaviour is treated as, in the main, determined by institutions and the structure of society. One element in the original Marxist doctrine would be of great importance for political theory, if there were any reason to suppose it true.