But the economist studies mental states rather through their manifestations than in themselves; and if he finds they afford evenly balanced incentives to action, he treats them prima facie as for his purpose equal.He follows indeed in a more patient and thoughtful way, and with greater precautions, what everybody is always doing every day in ordinary life.He does not attempt to weigh the real value of the higher affections of our nature against those of our lower: he does not balance the love for virtue against the desire for agreeable food.He estimates the incentives to action by their effects just in the same way as people do in common life.He follows the course of ordinary conversation, differing from it only in taking more precautions to make clear the limits of his knowledge as he goes.He reaches his provisional conclusions by observations of men in general under given conditions without attempting to fathom the mental and spiritual characteristics of individuals.But he does not ignore the mental and spiritual side of life.On the contrary, even for the narrower uses of economic studies, it is important to know whether the desires which prevail are such as will help to build up a strong and righteous character.And in the broader uses of those studies, when they are being applied to practical problems, the economist, like every one else, must concern himself with the ultimate aims of man, and take account of differences in real value between gratifications that are equally powerful incentives to action and have therefore equal economic measures.A study of these measures is only the starting-point of economics: but it is the starting-point.(2*)2.There are several other limitations of the measurement of motive by money to be discussed.The first of these arises from the necessity of taking account of the variations in the amount of pleasure, or other satisfaction, represented by the same sum of money to different persons and under different circumstances.
A shilling may measure a greater pleasure (or other satisfaction) at one time than at another even for the same person; because money may be more plentiful with him, or because his sensibility may vary.(3*) And persons whose antecedents are similar, and who are outwardly like one another, are often affected in very different ways by similar events.When, for instance, a band of city school children are sent out for a day's holiday in the country, it is probable that no two of them derive from it enjoyment exactly the same in kind, or equal in intensity.The same surgical operation causes different amounts of pain to different people.Of two parents who are, so far as we can tell, equally affectionate, one will suffer much more than the other from the loss of a favourite son.Some who are not very sensitive generally are yet specially susceptible to particular kinds of pleasure and pain; while differences in nature and education make one man's total capacity for pleasure or pain much greater than another's.
It would therefore not be safe to say that any two men with the same income derive equal benefit from its use; or that they would suffer equal pain from the same diminution of it.Although when a tax of ? is taken from each of two persons having an income of ?00 a year, each will give up that ? worth of pleasure (or other satisfaction) which he can most easily part with, i.e.each will give up what is measured to him by just ?;yet the intensities of the satisfaction given up may not be nearly equal.
Nevertheless, if we take averages sufficiently broad to cause the personal peculiarities of individuals to counterbalance one another, the money which people of equal incomes will give to obtain a benefit or avoid an injury is a good measure of the benefit or injury.If there are a thousand persons living in Sheffield, and another thousand in Leeds, each with about ?00a-year, and a tax of ? is levied on all of them; we may be sure that the loss of pleasure or other injury which the tax will cause in Sheffield is of about equal importance with that which it will cause in Leeds: and anything that increased all the incomes by ? would give command over equivalent pleasures and other benefits in the two towns.This probability becomes greater still if all of them are adult males engaged in the same trade;and therefore presumably somewhat similar in sensibility and temperament, in taste and education.Nor is the probability much diminished, if we take the family as our unit, and compare the loss of pleasure that results from diminishing by ? the income of each of a thousand families with incomes of ?00 a-year in the two places.
Next we must take account of the fact that a stronger incentive will be required to induce a person to pay a given price for anything if he is poor than if he is rich.A shilling is the measure of less pleasure, or satisfaction of any kind, to a rich man than to a poor one.A rich man in doubt whether to spend a shilling on a single cigar, is weighing against one another smaller pleasures than a poor man, who is doubting whether to spend a shilling on a supply of tobacco that will last him for a month.The clerk with ?00 a-year will walk to business in a much heavier rain than the clerk with ?00 a-year; for the cost of a ride by tram or omnibus measures a greater benefit to the poorer man than to the richer.If the poorer man spends the money, he will suffer more from the want of it afterwards than the richer would.The benefit that is measured in the poorer man's mind by the cost is greater than that measured by it in the richer man's mind.
But this source of error also is lessened when we are able to consider the actions and the motives of large groups of people.
