Marshall, commenting in 1908 on the Mathematical Appendix to his Principles, said: 'My whole life has been and will be given to presenting in realistic form as much as I can of my Note XXI.,5 Note XXI contains a general theory of distribution. Both as a scientist writing at a time when the question of who gets what was very much at the coal-face of economic research and as a modern missionary concerned with justice and about poverty and anxious to do good, Marshall was drawn as if by an invisible hand to the topics of remuneration and motivation with which this chapter and the four which follow it are concerned.