In an inquiry concerning the improvement of society, the mode of conducting  the subject which naturally presents itself, is, 

1. To investigate the causes that have hitherto impeded the progress of  mankind towards happiness; and, 
2. 2. To examine the probability of the total or partial removal of these  causes in future.

 To enter fully into this question, and to enumerate all the causes that  have hitherto influenced human improvement, would be much beyond the power of an individual. The principal object of  the present essay is to examin e the effects of one great cause intimately united with the very nature of man; which,  though it has been constantly and powerfully operating since the commencement of society, has been little noticed by the  writers who hav e treated this subject. The facts which establish the existence of this cause have, indeed, been repeatedly stated and  acknowledged; but its natural and necessary effects have been almost totally overlooked; though probably among these  effects may be reckoned a very considerable portion of that vice and misery, and of that unequal  distribution of the bounties of nature, which it has been the unceasing object of the enlightened philanthropist in all ages to  correct. 

The cause to which I allude, is the constant tendency in all animated life  to increase beyond the nourishment prepared for it. 

It is observed by Dr. Franklin, that there is no bound to the prolific  nature of plants or animals, but what is made by their crowding and interfering with each other's means of subsistence. Were  the face of the earth, he say s, vacant of other plants, it might be gradually sowed and overspread with one kind only, as for instance with fennel: and were it empty of other inhabitants, it might in a few ages be replenished from one nation only, as for inst ance with Englishmen. 

This is incontrovertibly true. Through the animal and vegetable kingdoms Nature has scattered the seeds of life abroad with the most profuse and liberal hand; but has been comparatively sparing in the room and the nourishment necessary to rea r them. The germs of existence contained in this earth, if they could freely develop themselves, would fill millions of worlds in the course of a few thousand years. Necessity, that imperious, all- pervading law of nature, restrains them wi thin the prescribed bounds. The race of plants and the race of animals shrink under this great restrictive law; and man cannot by any efforts of reason escape from it.

 In plants and irrational animals, the view of the subject is simple. They are all impelled by a powerful instinct to the increase of their species; and this instinct is interrupted by no doubts about providing for their offspr ing. Wherever therefore there is liberty, the power of increase is exerted; and the superabundant effects are repressed afterwards by want of room and nourishment. The effects of this check on man are more complicated. Impelled to the increase of his species by an equally powerful instinct, reason interrupts his career, and asks him whether he may not bring beings into the world, for whom he cannot provide the means of support. If he attend to this natural suggestion, th e restriction too frequently produces vice. If he hear it not, the human race will be constantly endeavouring to increase beyond the means of subsistence. But as, by that law of our nature which makes food necessary to the life of man, population can never actually increase beyond the lowest nourishment capable of supporting it, a strong check on population, from the difficulty of acquiring food, must be constantly in operation. This difficulty must fall somewhere,  and must necessarily be severely felt in some or other of the various forms of misery, or the fear of misery, by a large portion of mankind. 

That population has this constant tendency to increase beyond the means of subsistence, and that it is kept to its necessary level by these causes, will sufficiently appear from a review of the different states of society in which m an has existed. But, before we proceed to this review, the subject will, perhaps, be seen in a clearer light, if we endeavour to ascertain what would be the natural increase of population, if left to exert itself with perfect freedom; and what might be expected to be the rate of increase in the productions of the earth, under the most favourable circumstances of human industry.

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 According to a table of Euler, calculated on a mortality of I in 36, if the births be to the deaths in the proportion of 3 to 1, the period of doubling will be only 12 years and 4-5ths. And this proportion is not only a possible su pposition, but has actually occurred for short periods in more countries than one. 

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It may safely be pronounced, therefore, that population, when unchecked, goes on doubling it- self every twenty-five years, or increases in a geometrical ratio.

 The rate according to which the productions of the earth may be supposed to increase, it will not be so easy to determine. Of this, however, we may be perfectly certain, that the ratio of their increase in a limited territory must be of a totally different nature from the ratio of the increase of population. A thousand millions are just as easily doubled every twenty-five years by the power of population as a thousand. But the food to support the incre ase from the greater number will by no means be obtained with the same facility. Man is necessarily confined in room. When acre has been added to acre till all the fertile land is occupied, the yearly increase of food must depend upon the melioration of the land already in possession. This is a fund, which, from the nature of all soils, in- stead of increasing, must be gradually diminishing. But population, could it be supplied with food, would go on with unexh austed vigour; and the increase of one period would furnish the power of a greater increase the  next, and this without any limit. 

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It may be fairly pronounced, therefore, that, considering the present  average state of the earth, the means of subsistence, under circumstances the most favourable to human industry,  could not possibly be made to increase&nbs p;faster than in an arithmetical ratio. 

The necessary effects of these two different rates of increase, when  brought together, will be very striking. Let us call the population of this island eleven millions; and suppose the present  produce equal to the easy suppor t of such a number. In the first twenty-five years the population would be twenty-two  millions, and the food being also doubled, the means of subsistence would be equal to this increase. In the next  twenty-five years, the p opulation would be forty-four millions, and the means of subsistence only equal to the support  of thirty-three millions. In the next period the population would be eighty-eight millions, and the means of subsistence  just eq ual to the support of half that number. And, at the conclusion of the first century, the population would  be a hundred and seventy-six millions, and the means of subsistence only equal to the support of fifty-five millions,   ;leaving a population of a hundred and twenty- one millions totally unprovided for.

 Taking the whole earth, instead of this island, emigration would of course  be excluded; and, supposing the present population equal to a thousand millions, the human  species would increase as the numbers, 1, 2, 4, 8, 16 , 32, 64, 128, 256, and subsistence as 1, 2, 3, 4, 5, 6, 7,  8, 9. In two centuries the population would be to the means of subsistence as 256 to 9; in three centuries as 4096 to 13,  and in two thousand years the difference  would be almost incalculable. 

In this supposition no limits whatever are placed to the produce of the  earth. It may increase for ever and be greater than any assignable quantity; yet still the power of population being in  every period so much superior, th e increase of the human species can only be kept down to the level of the means of  subsistence by the constant operation of the strong law of necessity, acting as a check upon the greater power.