An Essay on the Principle of Population/Chapter IX

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An Essay on the Principle of Population  (1798) 
Thomas Malthus
London: Joseph Johnson pages 155-172


Mr. Condorcet's conjecture concerning the organic perfectibility of man, and the indefinite prolongation of human life.—Fallacy of the argument, which infers an unlimited progress from a partial improvement, the limit of which cannot be ascertained, illustrated in the breeding of animals, and the cultivation of plants.

The last question which Mr. Condorcet proposes for examination, is, the organic perfectibility of man. He observes, that if the proofs which have been already given, and which, in their development will receive greater force in the work itself, are sufficient to establish the indefinite perfectibility of man, upon the supposition, of the same natural faculties, and the same organization which he has at present; what will be the certainty, what the extent of our hope, if this organization, these natural faculties themselves, are susceptible of amelioration?

From the improvement of medicine; from the use of more wholesome food, and habitations; from a manner of living, which will improve the strength of the body by exercise, without impairing it by excess; from the destruction of the two great causes of the degradation of man, misery, and too great riches; from the gradual removal of transmissible and contagious disorders, by the improvement of physical knowledge, rendered more efficacious, by the progress of reason and of social order; he infers that though man will not absolutely become immortal, yet that the duration between his birth and natural death will increase without ceasing, will have no assignable term, and may properly be expressed by the word indefinite. He then defines this word to mean, either a constant approach to an unlimited extent, without ever reaching it; or, an increase in the immensity of ages to an extent greater than any assignable quantity.

But surely the application of this term in either of these senses, to the duration of human life, is in the highest degree unphilosophical and totally unwarranted by any appearances in the laws of nature. Variations from different causes are essentially distinct from a regular and unretrograde increase. The average duration of human life will, to a certain degree, vary from healthy or unhealthy climates, from wholesome or unwholesome food, from virtuous or vicious manners, and other causes; but it may be fairly doubted whether there is really the smallest perceptible advance in the natural duration of human life, since first we had any authentic history of man. The prejudices of all ages have indeed been directly contrary to this supposition, and though I would not lay much stress upon these prejudices, they will in some measure tend to prove, that there has been no marked advance in an opposite direction.

It may perhaps be said, that the world is yet so young, so completely in its infancy, that it ought not to be expected that any difference should appear so soon.

If this be the case, there is at once an end of all human science. The whole train of reasonings from effects to causes will be destroyed. We may shut our eyes to the book of nature, as it will no longer be of any use to read it. The wildest and most improbable conjectures may be advanced with as much certainty as the most just and sublime theories, founded on careful and reiterated experiments. We may return again to the old mode of philosophizing, and make facts bend to systems, instead of establishing systems upon facts. The grand and consistent theory of Newton, will be placed upon the same footing as the wild and eccentric hypotheses of Descartes. In short, if the laws of nature are thus fickle and inconstant; if it can be affirmed, and be believed, that they will change, when for ages and ages they have appeared immutable, the human mind will no longer have any incitements to inquiry, but must remain fixed in inactive torpor, or amuse itself only in bewildering dreams, and extravagant fancies.

The constancy of the laws of nature, and of effects and causes, is the foundation of all human knowledge; though far be it from me to say, that the same power which framed and executes the laws of nature, may not change them all "in a moment, in the twinkling of an eye." Such a change may undoubtedly happen. All that I mean to say is, that it is impossible to infer it from reasoning. If without any previous observable symptoms or indications of a change, we can infer that a change will take place, we may as well make any assertion whatever, and think it as unreasonable to be contradicted, in affirming that the moon will come in contact with the earth to-morrow, as in saying, that the sun will rise at its usual time.

With regard to the duration of human life, there does not appear to have existed, from the earliest ages of the world, to the present moment, the smallest permanent symptom, or indication of increasing prolongation.[1] The observable effects of climate, habit, diet, and other causes, on length of life, have furnished the pretext for asserting its indefinite extension; and the sandy foundation on which the argument rests, is, that because the limit of human life is undefined; because you cannot mark its precise term, and say so far exactly shall it go and no further; that therefore its extent may increase for ever, and be properly termed indefinite or unlimited. But the fallacy and absurdity of this argument will sufficiently appear from a slight examination of what Mr. Condorcet calls the organic perfectibility, or degeneration, of the race of plants and animals, which he says may be regarded as one of the general laws of nature.

I am told that it is a maxim among the improvers of cattle, that you may breed to any degree of nicety you please, and they found this maxim upon another, which is, that some of the offspring will possess the desirable qualities of the parents in a greater degree. In the famous Leicestershire breed of sheep, the object is to procure them with small heads and small legs. Proceeding upon these breeding maxims, it is evident, that we might go on till the heads and legs were evanescent quantities; but this is so palpable an absurdity, that we may be quite sure that the premises are not just, and that there really is a limit, though we cannot see it, or say exactly where it is. In this case, the point of the greatest degree of improvement, or the smallest size of the head and legs, may be said to be undefined, but this is very different from unlimited, or from indefinite, in Mr. Condorcet's acceptation of the term. Though I may not be able, in the present instance, to mark the limit, at which further improvement will stop, I can very easily mention a point at which it will not arrive. I should not scruple to assert, that were the breeding to continue for ever, the head and legs of these sheep would never be so small as the head and legs of a rat.

It cannot be true, therefore, that among animals, some of the offspring will possess the desirable qualities of the parents in a greater degree; or that animals are indefinitely perfectible.

The progress of a wild plant to a beautiful garden flower, is perhaps more marked and striking, than anything that takes place among animals, yet even here, it would be the height of absurdity to assert, that the progress was unlimited or indefinite.

One of the most obvious features of the improvement is the increase of size. The flower has grown gradually larger by cultivation. If the progress were really unlimited it might be increased ad infinitum; but this is so gross an absurdity, that we may be quite sure, that among plants, as well as among animals there is a limit to improvement, though we do not exactly know where it is. It is probable that the gardeners who contend for flower prizes have often applied stronger dressing without success. At the same time it would be highly presumptuous in any man to say, that he had seen the finest carnation or anemone that could ever be made to grow. He might however assert without the smallest chance of being contradicted by a future fact, that no carnation or anemone could ever by cultivation be increased to the size of a large cabbage; and yet there are assignable quantities much greater than a cabbage. No man can say that he has seen the largest ear of wheat, or the largest oak that could ever grow; but he might easily, and with perfect certainty, name a point of magnitude, at which they would not arrive. In all these cases therefore, a careful distinction should be made, between an unlimited progress, and a progress where the limit is merely undefined.

It will be said, perhaps, that the reason why plants and animals cannot increase indefinitely in size, is, that they would fall by their own weight. I answer, how do we know this but from experience? from experience of the degree of strength with which these bodies are formed. I know that a carnation, long before it reached the size of a cabbage, would not be supported by its stalk; but I only know this from my experience of the weakness, and want of tenacity in the materials of a carnation stalk. There are many substances in nature of the same size that would support as large a head as a cabbage.

The reasons of the mortality of plants are at present perfectly unknown to us. No man can say why such a plant is annual, another biennial, and another endures for ages. The whole affair in all these cases, in plants, animals, and in the human race, is an affair of experience; and I only conclude that man is mortal because the invariable experience of all ages has proved the mortality of those materials of which his visible body is made.

 "What can we reason, but from what we know?"

Sound philosophy will not authorize me to alter this opinion of the mortality of man on earth, till it can be clearly proved, that the human race has made, and is making, a decided progress towards an illimitable extent of life. And the chief reason why I adduced the two particular instances from animals and plants, was to expose, and illustrate, if I could, the fallacy of that argument, which infers an unlimited progress, merely because some partial improvement has taken place, and that the limit of this improvement cannot be precisely ascertained.

The capacity of improvement in plants and animals, to a certain degree, no person can possibly doubt. A clear and decided progress has already been made; and yet, I think it appears, that it would be highly absurd to say, that this progress has no limits. In human life, though there are great variations from different causes, it may be doubted, whether, since the world began, any organic improvement whatever in the human frame can be clearly ascertained. The foundations therefore, on which the arguments for the organic perfectibility of man rest, are unusually weak, and can only be considered as mere conjectures. It does not, however, by any means, seem impossible, that by an attention to breed, a certain degree of improvement, similar to that among animals, might take place among men. Whether intellect could be communicated may be a matter of doubt: but size, strength, beauty, complexion, and perhaps even longevity are in a degree transmissible. The error does not seem to lie, in supposing a small degree of improvement possible, but in not discriminating between a small improvement, the limit of which is undefined, and an improvement really unlimited. As the human race however could not be improved in this way, without condemning all the bad specimens to celibacy, it is not probable, that an attention to breed should ever become general; indeed, I know of no well-directed attempts of this kind, except in the ancient family of the Bickerstaffs, who are said to have been very successful in whitening the skins, and increasing the height of their race by prudent marriages, particularly by that very judicious cross with Maud, the milk-maid, by which some capital defects in the constitutions of the family were corrected.

It will not be necessary, I think, in order more completely to shew the improbability of any approach in man towards immortality on earth, to urge the very great additional weight that an increase in the duration of life would give to the argument of population.

Mr. Condorcet's book may be considered, not only as a sketch of the opinions of a celebrated individual, but of many of the literary men in France, at the beginning of the Revolution. As such, though merely a sketch, it seems worthy of attention.

  1. Many, I doubt not, will think that the attempting gravely to controvert so absurd a paradox, as the immortality of man on earth, or indeed, even the perfectibility of man and society, is a waste of time and words; and that such unfounded conjectures are best answered by neglect. I profess, however, to be of a different opinion. When paradoxes of this kind are advanced by ingenious and able men, neglect has no tendency to convince them of their mistakes. Priding themselves on what they conceive to be a mark of the reach and size of their own understandings, of the extent and comprehensiveness of their views; they will look upon this neglect merely as an indication of poverty, and narrowness, in the mental exertions of their contemporaries; and only think, that the world is not yet prepared to receive their sublime truths.

    On the contrary, a candid investigation of these subjects, accompanied with a perfect readiness to adopt any theory, warranted by sound philosophy, may have a tendency to convince them, that in forming improbable and unfounded hypotheses, so far from enlarging the bounds of human science, they are contracting it; so far from promoting the improvement of the human mind, they are obstructing it: they are throwing us back again almost into the infancy of knowledge; and weakening the foundations of that mode of philosophising, under the auspices of which, science has of late made such rapid advances. The present rage for wide and unrestrained speculation, seems to be a kind of mental intoxication, arising, perhaps, from the great and unexpected discoveries which have been made of late years, in various branches of science. To men elate, and giddy with such successes, every thing appeared to be within the grasp of human powers; and, under this illusion, they confounded subjects where no real progress could be proved, with those, where the progress had been marked, certain, and acknowledged. Could they be persuaded to sober themselves with a little severe and chastized thinking, they would see, that the cause of truth, and of sound philosophy, cannot but suffer by substituting wild flights and unsupported assertions, for patient investigation, and well authenticated proofs.