I am saying that the economic approach provides a valuable unified framework for understanding all human behaviour.

In attempting to understand the elements out of which mental phenomena are compounded, it is of the greatest importance to remember that from the protozoa to man there is nowhere a very wide gap either in structure or in behaviour. From this fact it is a highly probable inference that there is also nowhere a very wide mental gap.

In play, the child is always behaving beyond his age, above his usual everyday behaviour; in play he is, as it were, a head above himself. Play contains in a concentrated form, as in the focus of a magnifying glass, all developmental tendencies; it is as if the child tries to jump above his usual level.

As a rule, there is no surer way to the dislike of men than to behave well where they have behaved badly.

If a man, notoriously and designedly, insults and affronts you, knock him down; but if he only injures you, your best revenge is to be extremely civil to him in your outward behaviour, though at the same time you counterwork him, and return him the compliment, perhaps with interest.

At times unpopular measures are needed in order to change behaviour.