This we may call the #maxim of equality#, and equality consists in everybody paying, in one way or another, about an equal percentage of the wages, salary, or other income which he receives. In England the taxes amount to something like ten per cent., or one pound in every ten pounds, and this is pretty equally borne by different classes of society. It is probable, however, that the very rich do not pay as much as they ought to do. At the same time those who are too poor to pay income tax, and who do not drink nor smoke, are almost entirely free from taxation in this country; they pay very little, except poor rates. It would be impossible to invent any one tax which could be equally levied upon all persons. The income tax is a tax of so many pence in every pound of a person's income, but it is impossible to make people state their income exactly, and poor people could never be got to pay such a tax. Hence it is necessary to put on a certain number of different taxes so that those who manage to escape one tax shall be made to pay in some other way. (2) The tax which each individual is bound to pay ought to be certain, and not arbitrary. The time of payment, the manner of payment, the quantity to be paid, ought all to be clear and plain. This is the #maxim of certainty#, and it is very important, because, if a tax is not certainly known, the tax-gatherers can oppress people, requiring more or less as they choose. In this case it is very probable that they will become corrupt, and will receive bribes to induce them to lower the tax. On this account duties ought never to be levied according to the value of goods, or _ad valorem_, as it is said. Wine, for instance, varies in value immensely according to its quality and reputation, but it is impossible for the custom-house officer to say exactly what this value is. If he takes the statement of the people who import the wine, they will be tempted to tell lies, and say that the value is less than it really is. And as it would not be easy to prove the guilt either of the customs officer or of the importers, it is to be feared that some officers will receive bribes. But if the wine is taxed simply according to its quantity, the amount of duty is known with great certainty, and fraud can easily be detected. The same remarks apply more or less to every kind of goods which varies much in quality.