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LECTURE I. - Nassau William Senior, Two Lectures on Population, to which is added, a Correspondence between the Author and the Rev. T. R. Malthus 
Two Lectures on Population, delivered before the University of Oxford in Easter Term, 1828, to which is added, a Correspondence between the Author and the Rev. T. R. Malthus (London: Saunders and Otley, 1829).
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In the present and the following Lecture I propose to consider the subject of Population. A subject of which the details are almost endless, but the general principles few and plain. It is indebted probably to the latter circumstance for the degree in which it has attracted the public attention. The doctrines of rent, of value, and of money, are each as important as that of population, but they require the use of highly abstract terms, and depend on long chains of reasoning. They have, therefore, been avoided or neglected by many who are familiar, or suppose themselves to be familiar, with the simple laws of population. In my introductory Lecture I sketched what appeared to me an outline of those laws in the following proposition:—“That the population of a given district is limited only by moral or physical evil, or by deficiency in the means of obtaining those articles of wealth; or, in other words, those necessaries, decencies, and luxuries, which the habits of the individuals of each class of the inhabitants of that district lead them to require.”
The only modification which subsequent reflection induces me to apply to this proposition is, to substitute for the word “deficiency,” the words, “the apprehension of a deficiency.” My reasons for this substitution are: first, that the actual deficiency of necessaries is a branch of physical evil; and, secondly, that it is not the existence of a deficiency, but the fear of its existence which is the principal check to population, so far as necessaries are concerned, and the sole check as respects decencies and luxuries.
But before I take this proposition in detail, I feel that I ought to explain, as precisely as I can, what I mean by the words, necessaries, decencies, and luxuries; terms which have been used ever since the moral sciences first attracted attention in this country, but have never, within my knowledge, been defined.
It is scarcely necessary to remind you, that they are relative terms, and that some person must always be assigned, with reference to whom a given commodity or service is a luxury, a decency, or a necessary.
By necessaries then, I express those things, the use of which is requisite to keep a given individual in the health and strength essential to his going through his habitual occupations.
By decencies, those things which a given individual must use in order to preserve his existing rank in society.
Every thing else of which a given individual makes use; or, in other words, all that portion of his consumption which is not essential to his health and strength, or to the preservation of his existing rank in society, I term luxury.
It is obvious, that when consumed by the inhabitants of different countries, or even by different individuals in the same country, the same things may be either luxuries, decencies, or necessaries.
Shoes are necessaries to all the inhabitants of England. Our habits are such, that there is not an individual whose health would not suffer from the want of them. To the lowest class of the inhabitants of Scotland they are luxuries. Custom enables them to go barefoot without inconvenience and without degradation. When a Scotchman rises from the lowest to the middling classes of society they become to him decencies. He wears them not to preserve his feet, but his station in life. To the highest classes, who have been accustomed to them from infancy, they are as much necessaries as they are to all classes in England. To the higher classes in Asia wine is a luxury, and tobacco a decency. In Europe it is the reverse. The Asiatic drinks, and the European smokes, not in obedience but in opposition both to the rules of health, and to the forms of society. But wine in Europe and the pipe in Asia are among the refreshments to which a guest is entitled, and which it would be as indecent to refuse in the one country as to offer in the other.
It has been said that the coalheavers and lightermen, and some others among the hard working London labourers could not support their toils without the stimulus of porter. If this be true, porter is to them a necessary. To all others it is a luxury. A carriage is a decency to a woman of fashion, a necessary to a physician, and a luxury to a tradesman.
The question whether a given commodity is to be considered as a decency or a luxury, is obviously one to which no answer can be given, unless the place, the time, and the rank of the individual using it be specified. The dress which in England was only decent one hundred years ago, would be almost extravagant now; while the house and furniture, which now would afford only decent accommodation to a gentleman, would then have been luxurious for a peer.
The causes which entitle a commodity to be called a necessary, are more permanent and more general. They depend partly on the habits in which the individual in question has been brought up, partly on the nature of his occupation, on the lightness or the severity of the labours and hardships that he has to undergo, and partly on the climate in which he lives.
Of these causes I have illustrated the two first by the familiar examples of shoes and porter. But the principal cause is climate. The fuel, shelter, and raiment which are essential to a Laplander’s existence, would be worse than useless under the tropics. And as habits and occupations are very slowly changed, and climate suffers scarcely any alteration, the commodities which are necessary to the different classes of the inhabitants of a given district, may, and generally do, remain for centuries unchanged, while their decencies and luxuries are continually varying.
To recur, however, to my original proposition. I have stated, that the population of a given district is limited only by moral or physical evil, or by the apprehension of a deficiency of necessaries, decencies, or luxuries.
It is now generally admitted, indeed it is strange that it should ever have required to be pointed out, that every species of plant, or animal, which is capable of increase, either by generation, or by seed, must be capable of a constantly increasing increase; every addition to its numbers being capable of affording a source of still further additions, or, in other words, that wherever there is a capacity of increase, it must be a capacity of increase, not by mere addition, but by multiplication, or to use the shorter form in which the proposition is usually stated, not in an arithmetical, but in a geometrical ratio. The rate at which any species of plant, or animal, is capable of increasing, must depend on the average power of reproduction, and the average length of existence of the individuals of which it is constituted. Wheat, we know, is an annual, and its average power of reproduction perhaps about six for one. On that supposition the produce of a single acre might cover the globe in fourteen years.
The rate at which the human race is capable of increasing, has been determined by observation. It has been ascertained, that for considerable periods, and in extensive districts under temperate climates, it has doubled every twenty-five years.
The power of reproduction in the human race, must, under similar climates, be always and every where the same. I say, under similar climates, because the acceleration of puberty which has been sometimes observed in tropical countries, unless checked, as I believe to be the case, by an earlier cessation of child-bearing, would occasion increased fecundity. And the United States of America, the districts in which the rate of increase which I have mentioned has been most clearly ascertained, are not remarkable for the longevity of their inhabitants. We may infer, therefore, that such, at least, is the average power of reproduction, and average duration of life in the individuals constituting the human species, that their number may double every twenty-five years. At this rate the inhabitants of every country would, in the course of every five centuries, increase to above a million times their previous number. At this rate, the population of England, would, in five hundred years, exceed twelve millions of millions. A population which would approach the proportion of a family to every square inch of ground.
Such being the human powers of increase, the question is, by what checks is their expansion controlled? How comes it, that the population of the world, instead of being now a million times as great as it was five hundred years ago, apparently has not doubled within that time, and certainly has not quadrupled?
Mr. Malthus has divided the checks to population into the preventive and the positive. The first are those which limit fecundity, the second, those which decrease longevity. The first diminishes the number of births, the second increases that of deaths. And as fecundity and longevity are the only elements of the calculation, it is clear that Mr. Malthus’s division is exhaustive.
The positive check to population is physical evil. The preventive checks are promiscuous intercourse, and abstinence from marriage. The first is moral evil; the second is, with very few exceptions, so few that they do not affect the result, founded on an apprehended deficiency of necessaries, decencies, or luxuries, in other words, on prudence. All the preventive and positive checks, may, therefore, be distributed under prudence, moral evil, and physical evil. In the present lecture, I shall consider the positive, in the subsequent lecture the preventive, checks.
We have seen that the positive checks to population include all the causes which tend, in any way prematurely, to shorten the duration of human existence; such as unwholesome occupations, severe labour, or exposure to the seasons, bad or insufficient food or clothing, bad nursing of children, excesses of all kinds, the corruption of the air from natural causes, or from large towns, wars, infanticide, plague, and famine. Of these, some arise from the laws of nature, and others from the crimes and follies of man; all are felt in the form of physical evil, but the latter are the result of moral evil.
The final and irresistible mode in which physical evil operates, is the want of the necessaries of existence; death produced by hardship or starvation. This is almost the only check to the increase of the irrational animals, and as man descends towards their condition, he falls more and more under its influence. In the lowest savage state it is the principal and obvious check; in a high state of civilization it is almost imperceptible. But it is unperceived only in consequence of its substitutes.
We have seen that, as a general rule, additional labour employed in the cultivation of the land within a given district, produces a less proportionate return. And we have seen that such is the power of reproduction and duration of life in mankind, that the population of a given district is capable of doubling itself at least every twenty-five years. It is clear, therefore, that the rate at which the production of food is capable of being increased, and that at which population, if unchecked, would increase, are totally different. Every addition made to the quantity of food produced, makes, in general, a further addition more difficult. Every addition to the existing population, diffuses wider the means of still further addition. If neither evil, nor the fear of evil, checked the population of England, it would amount in a century to above two hundred millions. Supposing it possible that we might be able to raise, or to import the subsistence of two hundred millions of people, is it possible that a hundred and twenty-five years hence we should be able to support four hundred millions? or in a hundred and fifty years, eight hundred millions? It is clear, however, that long before the first century had elapsed—long before the period at which, if unchecked, we should have attained two hundred millions, no excellence in our institutions, or salubrity of climate, or unremitting industry, could have saved us from being arrested in our progress by a constantly increasing want of subsistence. If all other moral and physical checks could be got rid of, if we had neither wars, nor libertinism, if our habitations and employments and habits were all wholesome, and no fears of indigence, or loss of station prevented or retarded our marriages, famine would soon exercise her prerogative of controlling, in the last resort, the multiplication of mankind.
But though it be certain that the absence of all other checks would only give room for the irresistible influence of famine, it is equally certain that such a state of things never has existed, and never will exist.
In the first place, the absence of all the other moral and physical evils which retard population, implies a degree of civilization not only high, but higher than mankind have as yet enjoyed. Such a society cannot be supposed to want sagacity sufficient to foresee the evils of a too rapidly increasing population, and prudence sufficient to avert them, especially as that prudence might be exercised even by those who had no thought of public advantage, no idea of abstract reasoning, no care but for their private welfare. In such a state, the preventive check would be in full operation, and its force is quite sufficient to render unnecessary even the approach of any positive check.
And secondly, it is impossible that a positive check so goading and so remorseless as famine should prevail without bringing in her train all the others. Pestilence is her uniform companion, and murder and war are her followers. Whole bodies of men will not tamely lie down to die, and witness, while they are perishing, their wives and children and parents starving around them. Where there is a diversity of fortunes, famine generally produces that worst form of civil war, the insurrection of the poor against the rich. Among uncivilized nations it produces those tremendous hostile migrations in which a whole people throws itself across a neighbouring frontier, and either perishes in the attempt to obtain a larger or a more fertile territory, or destroys the former possessors, or drives them out to be themselves aggressors in turn.
In fact, almost all the positive checks by their mutual reaction have a tendency to create and aggravate one another: and the destruction of those who perish immediately by one, may generally be found to have been remotely occasioned by one or more of the others. Among nations imperfectly civilized, the widest and most wasting of the positive checks is predatory war. A district exposed to it must suffer in their full force all the others. Mere fear of invasion must keep them pent up in crowded and consequently unwholesome towns; it must confine their cultivation to the fields in the immediate neighbourhood of those towns; and if it do not destroy, must so much impede their commerce, as to render it useless as a source of subsistence. And when the invasion does come, it is often followed by the complete extirpation of the invaded community. This is the check which has kept the whole of Africa, the western parts of Asia, and the southern districts of America in their comparatively unpeopled state.
In his passage from Abyssinia to Sennaar, Bruce crossed the territory of Atbara, subject to the incursions of the Daveina Arabs. The whole country seems to have been a scene of desolation. He passed a night at Garigara, a village of which the crops had been destroyed a year before. The inhabitants had all perished with hunger, and their remains were unburied and scattered over the ground where the village had stood. The travellers encamped among the bones: no space could be found free from them. His next stage was Teawa. “Its consequence,” he observes, “was to remain only till the Daveina Arabs should resolve to attack it; when its corn-fields being burnt and destroyed in a night by a multitude of horsemen, the bones of its inhabitants, scattered upon the earth, would be all its remains, like those of the miserable village of Garigara.”
Among the positive checks to the population of uncivilized, or partially civilized nations, the next in importance to war is famine.
I have already observed, that there is so much reaction among the positive checks, that one of them alone is seldom experienced. But when a people depends principally on that subsistence which is most abundant, (and such is the case among the nations in question,) the mere variations of the seasons must, from time to time, produce destructive want. Where society is better constituted, the evil of these variations is mitigated, partly from the superfluity of the more opulent classes, partly by importation, and principally by a recurrence to a less expensive diet; but in a barbarous, and consequently a poor and uncommercial country, they are the most frightful forms of national calamity. The histories which we possess of such countries, always particularize periods of dearth as amongst the most memorable events recorded. They seem in a constant oscillation, between the want endured by a population that has increased to the utmost limits of subsistence, and the plenty enjoyed by the survivors, after that population has been thinned by war, pestilence, or famine.
The remainder of the positive checks, such as infanticide, and unwholesomeness of climate, habits, or situation, appear rather to act as substitutes for the preventive checks, than to produce any actual diminution, or prevent any actual increase.
Infanticide has been supposed to be rather favourable to population, by opposing to the prudential check to marriage a mode of disposing of its offspring, which may appear easy in contemplation, but from which the feelings of the parents eventually recoil. The unwholesomeness of some districts is unquestionably such, as to keep them totally unpeopled, or inhabited by strangers, whose numbers must be constantly recruited. Such, for instance, appears to be the case in the most unhealthy parts of Italy; and such is the case with large manufacturing towns, even in the most favourable climates, unless great skill and great care are directed towards their cleanliness and ventilation. And in a newly colonized country, like the back settlements in America, where the abundance of land, and the constantly increasing means of subsistence, would render any preventive check unnecessary, any cause diminishing longevity must retard increase. But, with these exceptions, unhealthiness rather causes the successive generations of mankind to pass more rapidly away, than diminishes their actual number. In some of the healthiest districts of Switzerland, the average annual mortality does not exceed one in fifty; in many of the marshy villages of Holland it exceeds one in twenty-three. But it would be rash to expect the population of the former to be more dense, or to increase more rapidly, than that of the latter. The case is, in fact, the reverse. In the Swiss villages of which I have been speaking, the births are as rare as the deaths: the population is thin and stationary. Among the Dutch the births somewhat exceed the deaths: the population is dense, and is increasing. It is obvious indeed, that the proportion of annual births to the whole number of people being given, the rate of increase must depend on the proportion borne by the annual deaths. And the proportion of deaths to the whole number of people being given, it must depend on the proportion borne by the births; or, to use a shorter form of expression, given the longevity, it must depend on the fecundity; and given the fecundity, it must depend on the longevity. If both are given, the rate of increase may be calculated; but from only one the conclusion must be the disjunctive. If the annual births bear a large proportion to the existing number of people, we may conclude either that the population is rapidly increasing, or that the positive checks are in powerful operation. On the other hand, from a small proportion of annual deaths may be inferred either a rapid increase of numbers, or a strong prevalence of the preventive checks. The average duration of life in England is greater than in the United States of America; but so much greater is the force of the preventive checks, that the rate of increase in America is double that in England. Again, the average duration of life in the Swiss villages that I have before referred to, is the same as it is in England; but the preventive check in England, strong as it appears when compared with its force in America, is so much weaker than it is in some districts in Switzerland that with the same annual mortality the population is in the one country stationary, in the other rapidly progressive.
But although the average longevity in a country affords no decisive evidence as to the increasing or stationary number of its inhabitants, it is among the least deceitful tests of their prosperity: far less so than that on which statesmen formerly relied, the number of births. There is not an evil, moral or physical, which has not a tendency, directly or indirectly, to shorten life, but there are many which have a direct tendency to increase fecundity. The extraordinary duration of life in England, exceeding, as it does, the average of any other equally extensive district, is a convincing proof of the general excellence of our climate, our institutions, and our habits.
In my next Lecture I shall consider the preventive checks to population.