This rule, indeed, does not apply to the schemers, speculators, or #promoters#, as they are called, who start so many companies. These people make it their business to have new schemes and shares to offer just when people are in a mind to buy, that is, during a bubble or time of excited trade. They take care to sell their own shares before the collapse comes, and it is their dupes who bear all the loss. A prudent man, therefore, would never invest in any new thing during a mania or bubble; on the contrary, he would sell all property of a doubtful or speculative value, when its price is high, and invest it in the very best shares or government funds, of which the value cannot fall much during the coming collapse. The wisest men have been deluded during manias; and in the Library of the Royal Society is shown a letter from Sir Isaac Newton requesting a friend to buy shares for him in the South Sea Company, just at the moment when the South Sea Bubble was at its worst. Let people take warning by Sir Isaac Newton, and never speculate in a thing because other people are doing the same; then these bubbles and collapses will be prevented, or will become much less disastrous. Credit cycles will go on until the public learn to look out for them, and act accordingly. Business men must become bold during depressed trade, careful during excited trade, instead of acting exactly in the opposite way. It is only a knowledge of these credit cycles which can prevent them, and this is the reason why I have said so much about them in this Primer. CHAPTER XV. THE FUNCTIONS OF GOVERNMENT. 92. Functions mean performances (Latin, _fungi_, _functus_, to perform), and the functions of government mean those things which a government ought to do,--the duties which it undertakes to perform, or the services which it may be expected to render to the people governed. These functions are commonly divided into two classes-- (1) The necessary functions. (2) The optional functions. The #necessary functions# of a government are such as it is obliged to undertake; thus it must defend the nation against foreign enemies, it must keep the peace within the country, and prevent insurrections which might threaten the existence of the government itself; it must also punish evildoers who break the laws, and try to become rich by robbery; it must also maintain law courts in which the disputes of its subjects can be fairly decided, and set at rest. These are far from being all the necessary functions.