Wicksteed on Marginalism

Some wonderful quotes from Common Sense, in which Philip Wicksteed explains marginalism as it applies to household management, brought to my attention by Sandra Peart and David Levy:

This task of home administration is not of uniform difficulty. Materfamilias will not mind who gets hold of the bread though she will exercise a general watchfulness against its being wasted, but when she has begun her first purchases of new potatoes for the year, she will be very careful to keep the dish under her own direct control and not let one of the children determine, at his own discretion, what is his proper share; for if she did there would be disproportionate gratification and disproportionate privation. “I am as the centre of the circle to which all parts of the circumference bear a like relation. But thou art not such,” she says in effect to each child in turn. She may let the milk-jug pass freely round, and her vigilance will only take note of mugs full, but she will keep the cream-jug in her own immediate vicinity, and however nobly she tilts it on some occasions, there will be others on which she measures and estimates its contents by drops. But in all cases, whether she is spending money, helping the potatoes, pouring out the cream, or exercising a more general vigilance over the bread and milk, she is engaged in the same problem of the administration of resources and she is guided by the same principle. She is trying to make everything go as far as it will, or, in other words, serve the most important purpose that it can. She will consider that she has been successful if, in the end, no want which she has left unsatisfied appears, in her deliberate judgment, to have really been more important than some other want to which she attended in place of it. Otherwise there has been waste somewhere, for money, milk, potatoes, or attention have been applied to one purpose when they might better have been applied to another. (1.1.12)

Note that “attention” is included amongst the things that have to be administered and that are often wasted. The art of life includes the art of effectively and economically distributing our vital resources of every kind, and domestic administration is a branch of this art in which it is possible to pay too dear in money for the saving of time, or too dear in time for the saving of money, or too dear in thought and energy for saving in bread, potatoes, or cream. Whatever the nature of the alternatives before us, the question of the terms on which they are offered is always relevant. If we secure this, how much of that must we pay for it, or what shall we sacrifice to it? And is it worth it? What alternatives shall we forgo? And what would be their value to us? (1.1.12)

Let us examine this principle further. We have seen, in comparing the different applications of milk in an ordinary middle-class family, that if the administration is ideally carried out, the significance of the last small increments of milk are equal in all its ordinary applications. The first thimbleful of milk given to the baby is immensely more significant than the first thimbleful given to the children or reserved for afternoon tea; but if the last thimbleful given to the cat does not perform as important a service as the last thimbleful given to the children, there would have been a gain in giving her a little less and them a little more; and there has therefore been a failure in administration. The cost of giving more to one applicant is giving less to another, and good administration consists in avoiding any application which costs more than it is worth. But as well as balancing all the uses of milk, at the margin, one against the other, the housekeeper has to balance them all, collectively, against every other alternative expenditure of the money she paid for milk, and this opens up another source of possible mistake. In taking in the milk for the day or half-day the housewife considers, consciously or unconsciously, what the significance of the last thimblefuls applied to all the varied purposes, when properly balanced, will be. The answer to the question, “How much milk shall we take to-day, ma'am?” depends on a rapid survey of the programme of the day. If milk is 4d. a quart, the aim is to take in such an amount that the last half-pint shall be just worth 1d.; that is to say, the last thimblefuls in every application, brought into equilibrium of marginal significance with each other, should collectively be worth just as much as anything else on which the 1d. might be spent. (1.2.79)

But unforeseen contingencies may arise. There may be a great ink-spill, and milk may be wanted to take out the stain while fresh. A little sapling, laden with many associations, may arrive, to grow in the garden or yard, and some one may have read that milk comforts and revives the roots of trees that have felt a journey. The dog may have eaten phosphorous poison, and some one may know that the proper remedy is to drench him with milk. And these sudden and unexpected claims have not been anticipated or provided for. It may really be the case (especially if you live in the country) that more milk cannot, without great difficulty, be got for some hours; or if you live in the town, it does not occur to you (owing to mental inertia) that there is any way of getting more milk except the customary one of waiting till the milk-man comes round again. And so a new set of claimants on the day's supply of milk, of which there was no thought when the milk was taken in, has been introduced. In the case of the poisoned dog, it might well be that even the baby would be put on short allowance for a certain period, or driven to some substitute, in the hope of saving the life of an inmate of the house, whose loss would be long and sincerely mourned. Now it may be perfectly understood that there are always such risks, but it is bad economy to provide for a risk as though it were a certainty, and therefore when such a contingency occurs it will set up an urgent demand for which it would not have been reasonable to make provision. It must therefore be met out of the general stock, and all the other uses will be trenched upon. The last thimblefuls will still be kept in equilibrium, but each will meet a more clamorous demand than usual, the lower or less clamorous demands not being met at all; and if the dog has been poisoned, probably the cat will get nothing, even her initial and most urgent claim not being able to compete for a place amongst the higher demands that alone can be satisfied now. (1.2.79)