Keynes saw Malthus as a predecessor. In this, I think he was wrong--or perhaps I should say that Keynes was much more Malthusian than the parts of him we pull out and focus on today.

When Malthus talks of a "general glut" of commodities, or a "universal glut", or a "glut", he is rarely referring to something we would call business-cycle unemployment. Instead, he is typically talking about:

high production of manufactured non-necessities...

low demand for manufactured non-necessities, usually induced by "thrift"--which to Malthus means both a high savings rate and a reduction in demand for non-necessities...

consequently, a low price of manufactured non-necessities...

perhaps the low price of manufactured non-necessities leads to a restricted variety of non-necessities being produced--which further lowers demand for them as satiation rapidly sets in...

low real wages for the working class, whose wages are largely set in manufacturing...

"indolence" on the part of a working class whose real wages are low...

The context is that of post-Napoleonic Wars Britain, where the end of the war effort has produced, Malthus says, a very sharp and permanent reduction in demand for necessities. Malthus is arguing against economists who call for more "thrift" in order to build up the capital stock, boost real wages, and employ the idle. For Malthus, "thrift" means both (a) savings in order to boost the capital stock, and (b) cutting back on consumption of non-necessities. Because Malthus does not think these two meanings of "thrift" can be separated, he thinks that the argument that what post-Napoleonic Britain needs is more thrift is simply wrong.

Jean-Baptiste Say and Say's Law typically enter Malthus's argument as a rebuttal to a counter-argument. Malthus's adversaries admit to low employment and low wages in post-Napoleonic Britain, but say that they reflect not any permanent defect or deficiency in the market system but are rather due to a temporary planning error by manufacturers, who have produced too much in too narrow a range of industries. Malthus counters that Say's Law claims that an excess supply of one commodity must be offset by an excess demand for another:

[I]t is a tenet of the new doctrine on profits and demand that if one trade be overstocked with capital it is a certain sign that some other trade is understocked. But where, I would ask, is there any considerable trade that is confessedly under-stocked, and where high profits have been long pleading in vain for additional capital? The war has now been at an end above four years; and though the removal of capital generally occasions some partial loss, yet it is seldom long in taking place, if it be tempted to remove by great demand and high profits...

Thus, Malthus concludes, the poorly-paid and idle dangerous classes of post-Napoleonic Britain pose a long-term problem that cannot be resolved by calling for more thrift and more capital accumulation to boost labor productivity, and thus real wages and employment. It seems more true to Malthus to say that he admits that Say's Law holds in a business-cycle planning-error context in order to deny that high post-Napoleonic War unemployment and the "glut" of cotton manufactured goods are a transitory business-cycle problem.

Keynes sees Malthus as a predecessor because Keynes sees Malthus as denying Say's Law. And you can certainly find a paragraph or two of his argument that sounds proto-Keynesian. But the main thrust of Malthus's argument is an a direction very different from that of our modern concerns with business-cycle unemployment.

Malthus on "glut": all the mentions I have found:

Remarks on Ricardo's Theory of Profits:

Remarks on Mr. Ricardo's Theory of Profits: Adverting to the known effects of permanent improvements on the land... [a] extensive territory... capable of cultivation, might, by continued improvements in agriculture, admit of the employment of a vast mass of capital for hundreds of years, with little or with no fall of profits; while the small but fertile territory, being very soon filled with all the capital it could employ on the land, would be obliged to employ its further accumulations in the purchase of corn with falling manufactures; a state of things which might easily reduce profits to their lowest rate.... A country, which accumulates faster... might for hundreds of years still keep up its rate of profits, if it were successful in making permanent improvements on the land; but, if with the same rapidity of accumulation it were to depend chiefly on imported corn, its profits could scarcely fail to fall... by a fall in the bullion price of the exports with which the corn was purchased by the country in question. These statements appear to me to accord with the most correct theory of profits, and they certainly seem to be confirmed by experience.... [T]he effect of falling [manufacturing export] prices in reducing profits is but too evident at the present moment. In the largest article of our exports, the wages of labour are now lower than they probably would be in an ordinary state of things if corn were at fifty shillings a quarter. If, according to [Ricardo's] new theory of profits, the prices of our exports had remained the same, the master manufacturers would have been in a state of the most extraordinary prosperity, and the rapid accumulation of their capitals would soon have employed all the workmen that could have been found. But, instead of this, we hear of glutted markets, falling prices, and cotton goods selling at Kamschatka lower than the costs of production. It may be said, perhaps, that the cotton trade happens to be glutted; and it is a tenet of the new doctrine on profits and demand, that if one trade be overstocked with capital, it is a certain sign that some other trade is understocked. But where, I would ask, is there any considerable trade that is confessedly under-stocked, and where high profits have been long pleading in vain for additional capital? The war has now been at an end above four years; and though the removal of capital generally occasions some partial loss, yet it is seldom long in taking place, if it be tempted to remove by great demand and high profits; but if it be only discouraged from proceeding in its accustomed course by falling profits, while the profits in all other trades, owing to general low prices, are falling at the same time, though not perhaps precisely in the same degree, it is highly probable that its motions will be slow and hesitating...

Much more a statement about a low elasticity of demand for Britain's manufacturing exports, and thus a claim that capital accumulation in manufacturing will not keep British wages from falling as population increases, than a statement about cyclical unemployment and its causes. The word "glut" enters into the argument as part of a rebuttal to the counterargument that the reason that profits and wages in cotton export manufacturing are so low is because employers guessed wrong and produced too much in too narrow a range of industries.

Principles of Political Economy: "general glut": one match:

Principles of Political Economy: Mr. Ricardo was... the first writer... to make a marked distinction between wealth and value... he has made the distinction much broader than it really is. If the great measure of the exchangeable value of a commodity... depend[ed] exclusively upon difficulty of production... its power of measuring wealth would be extremely imperfect: while, if the great measure... is... the quantity of labour which it will command, such a measure will be found to be very much more comprehensive, and to make much nearer approaches to a measure of wealth.... [T]he general causes of a permanent nature which are most effective in the production of wealth will be found also the most effective in the production of value; and in reference to the whole produce of a country, quantity seldom fails to increase value, except in those temporary cases of a general glut, in which it must be allowed that even the wealth of a country is far from being proportioned to the increased quantity of the commodities it has produced...

The phrase "general glut" is used in Malthus's admission that his idea of using consumer value rather than producer cost as a measure of wealth will only work in normal times--not in times of high business cycle unemployment and fire-sale prices.

Principles of Political Economy: "glut": other matches:

Principles of Political Economy: But we have yet to inquire what is the state of things which generally disposes a nation to accumulate; and... what is the state of things which tends to make that accumulation the most effective, and lead to a further and continued increase of capital and wealth. It is undoubtedly possible by parsimony to devote at once a much larger share than usual of the produce of any country to the maintenance of productive labour... labourers so employed are consumers as well.... But it has already been shewn that the consumption and demand occasioned by the workmen employed in productive labour can never alone furnish a motive to the accumulation and employment of capital... the capitalists themselves, together with the landlords and other rich persons... have, by the supposition, agreed to be parsimonious... depriving themselves of their usual conveniencies and luxuries to save from their revenue and add to their capital. Under these circumstances, it is impossible that the increased quantity of commodities, obtained by the increased number of productive labourers, should find purchasers, without such a fall of price as would probably sink their value below that of the outlay, or, at least, so reduce profits as very greatly to diminish both the power and the will to save. It has been thought by some very able writers, that although there may easily be a glut of particular commodities, there cannot possibly be a glut of commodities in general; because, according to their view of the subject, commodities being always exchanged for commodities, one half will furnish a market for the other half, and production being thus the sole source of demand, an excess in the supply of one article merely proves a deficiency in the supply of some other, and a general excess is impossible. M. Say, in his distinguished work on political economy, has indeed gone so far as to state that the consumption of a commodity by taking it out of the market diminishes demand, and the production of a commodity porportionably increases it. This doctrine, however, as generally applied, appears to me to be utterly unfounded.... It is by no means true, as a matter of fact, that commodities are always exchanged for commodities. An immense mass... is exchanged... for productive labour or personal services: and it is quite obvious that this mass... compared with the labour with which it is to be exchanged, may fall in value from a glut.... In the case supposed there would evidently be an unusual quantity of commodities of all kinds in the market, owing to those who had been before engaged in personal services having been converted, by the accumulation of capital, into productive labourers... commodities would necessarily fall in value compared with labour, so as very greatly to lower profits, and to check for a time further production. But this is precisely what is meant by the term glut, which, in this case, is evidently general not partial...

Appears to be much more a statement about the elasticity of demand for commodities in general--that perhaps an increase in productivity leads not to an increase in output but instead to a sharp increase in leisure because consumers rapidly become satiated with necessities. Not a statement about business-cycle unemployment at all.

Mr. Ricardo... maintains... that capital cannot be redundant, is obliged to make the following concession.... There is only one case, and that will be temporary, in which the accumulation of capital with a low price of food may be attended with a fall of profits; and that is, when the funds for the maintenance of labour increase much more rapidly than population;--wages will then be high and profits low. If every man were to forego the use of luxuries and be intent only on accumulation, a quantity of necessaries might be produced for which there could not be any immediate consumption. Of commodities so limited in number, there might undoubtedly be an universal glut; and consequently there might neither be demand for an additional quantity of such commodities, nor profits on the employment of more capital. If men ceased to consume, they would cease to produce. Mr. Ricardo then adds, This admission does not impugn the general principle. In this last remark I can by no means agree with him. It appears to me most completely to impugn the general principle.... [I]f, whenever this occurs, there may be an universal glut of commodities, how can it be maintained, as a general position, that capital is never redundant; and that because commodities may retain the same relative values, a glut can only be partial, not general?...

Malthus pounces on Ricardo's admission that higher labor productivity produced by capital accumulation must be accompanied by a shift in production to non-necessities and away from necessities or else there will be a universal glut.

Another fundamental error into which the writers above-mentioned and their followers appear to have fallen is, the not taking into consideration the influence of so general and important a principle in human nature, as indolence or love of ease. It has been supposed that, if... powers of production were suddenly so increased that both parties could, with the same labour, produce luxuries in addition to what they had before obtained, there could be no sort of difficulty with regard to demand, as part of the luxuries which the farmer produced would be exchanged against part of the luxuries produced by the manufacturer; and the only result would be, the happy one of both parties being better supplied and having more enjoyments. But in this intercourse of mutual gratifications, two things are taken for granted, which are the very points in dispute. It is taken for granted that luxuries are always preferred to indolence, and that an adequate proportion of the profits of each party is consumed as revenue.... The effect of a preference of indolence to luxuries would evidently be to occasion a want of demand for the returns of the increased powers of production supposed, and to throw labourers out of employment. The cultivator, being now enabled to obtain the necessaries and conveniences to which he had been accustomed, with less toil and trouble, and his tastes for ribands, lace and velvet not being fully formed, might be very likely to indulge himself in indolence... while the manufacturer, finding his velvets rather heavy of sale, would be led to discontinue their manufacture, and to fall almost necessarily into the same indolent system.... [I]t is a most important error to take for granted, that mankind will produce and consume all that they have the power to produce and consume, and will never prefer indolence to the rewards of industry, will sufficiently appear from a slight review of some of the nations with which we are acquainted.... It has been said... that if the idle were made to produce the surplus would disappear. But... [t]he real question is, whether under the actual habits and tastes of the society... persons... inclined to save and produce... would be secure of finding such a demand for all they could bring into the market as to prevent the possibility of what is called a glut, or a great fall of profits in a large mass of commodities. What might happen under different tastes and habits is entirely a different question. It has also been said, that there is never an indisposition to consume, that the indisposition is to produce. Yet, what is the disposition of those master manufacturers, and merchants who produce very largely and consume sparingly? Is their will to purchase commodities for their consumption proportioned to their power? Does not the use which they make of their capital clearly show that their will is to produce, not to consume? and in fact, if there were not in every country some who were indisposed to consume to the value of what they produced, how could the national capital ever be increased?...

Once again, a glut is the satiation of demand for necessities, thus a low price of commodities relative to leisure, and thus "indolence"--a leisured society.

A third very serious error... consists in supposing that accumulation ensures demand.... Ricardo observes, that “If £10,000 were given to a man having £100,000 per annum, he would not lock it up in a chest, but would either increase his expenses by £10,000, employ it himself productively, or lend it to some other person for that purpose.... Upon this principle it is supposed that if the richer portion of society were to forego their accustomed conveniences and luxuries with a view to accumulation, the only effect would be a direction of nearly the whole capital of the country to the production of necessaries, which would lead to a great increase of cultivation and population. But this is precisely the case in which Mr. Ricardo distinctly allows that there might be a universal glut; for there would undoubtedly be more necessaries produced than would be sufficient for the existing demand. This state of things could not, however, continue; since, owing to the fall which would take place, cultivation would be checked, and accumulation be arrested in its progress. It is therefore obvious that without an expenditure which will encourage commerce, manufactures, and personal services, the possessors of land would have no sufficient stimulus to cultivate well; and a country such as our own, which had been rich and populous, would, with too parsimonious habits, infallibly become poor and comparatively unpeopled.... An accumulation... of common food and common clothing might take place on both sides; but the amount must necessarily be extremely confined. It would be no sort of use to the farmer to go on cultivating his land with a view merely to give food and clothing to his labourers. He would be doing nothing either for himself or family, if he neither consumed the surplus of what they produced himself, nor could realize it in a shape that might be transmitted to his descendants.... It would be still more useless to the manufacturers to go on producing clothing beyond what was wanted by the agriculturists and themselves.... The population required to provide simple clothing for such a society with the assistance of good machinery would be inconsiderable, and would absorb but a small portion of the proper surplus of rich and well cultivated land. There would evidently therefore be a general want of demand, both for produce and population; and while it is quite certain that an adequate passion for consumption may fully keep up the proper proportion between supply and demand... it appears to be quite as certain that an inordinate passion for accumulation must inevitably lead to a supply of commodities beyond what the structure and habits of such a society will permit to be profitably consumed. But if this be so, surely it is a most important error to couple the passion for expenditure and the passion for accumulation together, as if they were of the same nature; and to consider the demand for the food and clothing of the labourer, who is to be employed productively, as securing such a general demand for commodities and such a rate of profits for the capital employed in producing them, as will adequately call forth the powers of the soil, and the ingenuity of man in procuring the greatest quantity both of raw and manufactured produce.... It is not, of course, meant to be stated that parsimony, or even a temporary diminution of consumption, is not often in the highest degree useful, and sometimes absolutely necessary to the progress of wealth. A state may certainly be ruined by extravagance.... All that is contended for is, that no nation can possibly grow rich by an accumulation of capital, arising from a permanent diminution of consumption; because such accumulation being beyond what is wanted in order to supply the effectual demand for produce, a part of it would very soon lose both its use and its value, and cease to possess the character of wealth...

Once again, a statement higher labor productivity produced by capital accumulation must be accompanied by a shift in production to luxuries away from necessities. "Thrift" here means two things: (a) higher savings that are invested in expanding the economy's produced means of production; and (b) reduced consumption of non-necessities. Because Malthus runs these two meanings together rather than separating them, he sees a big problem.

It is the natural tendency of foreign trade... immediately to increase the value of that part of the national revenue which consists of profits, without a proportionate diminution elsewhere... from the exchange of what is of less value in the country, for what is of more value... [that] is a striking and almost universal accompaniment of successful foreign commerce; whereas a mere abundance of commodities falling very greatly in value compared with labour, though it may be called an actual increase of wealth, would obviously at first diminish the power of employing the same number of workmen, and a temporary glut and general deficiency of demand could not fail to ensue in labour, in produce, and in capital, attended with the usual distress which a glut must necessarily occasion. Mr. Ricardo always views foreign trade in the light of means of obtaining cheaper commodities. But this is only looking to one half of its advantages, and... not the larger half.... The great mass of our imports consists of articles as to which there can be no kind of question about their comparative cheapness, as raised abroad or at home. If we could not import from foreign countries our silk, cotton and indigo, our tea, sugar, coffee and tobacco, our port, sherry, claret and champagne, our almonds, raisins, oranges and lemons, our various spices and our various drugs, with many other articles peculiar to foreign climates, it is quite certain that we should not have them at all. To estimate the advantage derived from their importation by their cheapness, compared with the quantity of labour and other advances which they would have cost, if we had attempted to raise them at home, would be perfectly preposterous. In reality, no such attempt would have been thought of. If we could by possibility have made fine claret at ten pounds a bottle, few or none would have drunk it; and the actual quantity of labour and other advances employed in obtaining these foreign commodities is at present beyond comparison greater than it would have been if we had not imported them. We must evidently therefore estimate the advantage which we derive from such a trade upon a very different principle. This is the simple and obvious one often adverted to as the foundation of every act of barter, whether foreign or domestic, namely, the increased value which results from exchanging what is wanted less for what is wanted more.... [W]e might be very much puzzled to say whether we had increased or decreased the quantity of our commodities, but we should feel quite certain that the new distribution of produce... giving us commodities much better suited to our wants and tastes... had decidedly increased the exchangeable value of our possessions, our means of enjoyment, and our wealth.

Here both meanings are run together. A glut is a low price of commodities relative to leisure and "indolence"--a leisured society. And foreign trade can avoid a glut by enabling the consumption of extra varieties of luxuries, thus fending off satiation.

It has been said that the distresses of the labouring classes since 1815 are owing to a deficient capital, which is evidently unable to employ all that are in want of work.... But it is a very different thing to allow that the capital is deficient compared with the population; and to allow that it is deficient compared with the demand for it, and the demand for the commodities procured by it. The two cases are very frequently confounded, because they both produce distress among the labouring classes; but they are essentially distinct.... If one fourth of the capital of a country were suddenly destroyed... this scantiness of capital would certainly occasion great inconvenience to consumers, and great distress among the working classes; but it would be attended with great advantages to the remaining capitalists. Commodities, in general, would be scarce, and bear a high price.... Nothing would be so easy as to find a profitable employment for capital... the rate of profits would be very high. In this state of things there would be an immediate and pressing demand for capital... and the obvious remedy would be... saving from revenue to add to capital.... On the other hand, if the capital of the country were diminished by the failure of demand in some large branches of trade, which had before been very prosperous... the state of things, with the exception of the distresses of the poor, would be almost exactly reversed. The remaining capitalists would be in no respect benefited.... Commodities would be every where cheap. Capital would be seeking employment, but would not easily find it; and the profits of stock would be low. There would be no pressing and immediate demand for capital... saving from revenue to add to capital, instead of affording the remedy required, would only aggravate the distresses.... The distresses of the capitalists would be aggravated, just upon the same principle as the distresses of the labouring classes would be aggravated if they were encouraged to marry and increase, after a considerable destruction of people, although accompanied by a still greater destruction of capital which had kept the wages of labour very low. There might certainly be a great deficiency of population, compared with the territory and powers of the country... but if the wages of labour were still low, notwithstanding the diminution of people, to encourage the birth of more children would be to encourage misery and mortality rather than population. Now I would ask, to which of these two suppositions does the present state of this country bear the nearest resemblance? Surely to the latter.... The two last years of the war were... years of extraordinary expense.... [The troubles] commenced certainly with the extraordinary fall in the value of the raw produce of the land.... When this fall had diminished the capitals of the farmers, and still more the revenues both of landlords and farmers... their power of purchasing manufactures and foreign products was of necessity greatly diminished. The failure of home demand filled the warehouses of the manufacturers with unsold goods, which urged them to export more largely at all risks. But this excessive exportation glutted all the foreign markets, and prevented the merchants from receiving adequate returns; while, from the diminution of the home revenues, aggravated by a sudden and extraordinary contraction of the currency, even the comparatively scanty returns obtained from abroad found a very insufficient domestic demand, and the profits and consequent expenditure of merchants and manufacturers were proportionably lowered. While these unfavourable changes were taking place in rents and profits, the powerful stimulus which had been given to population by the continued demand for labour during the war, occasioned the pouring in of fresh supplies of labour, which, aided by the disbanded soldiers and sailors... reduced generally both wages and profits... the population, under its former impulse, has increased, not only faster than the demand for labour, but faster than the actual produce; yet this produce, though deficient, compared with the population, is redundant, compared with the effectual demand for it and the revenue which is to purchase it. Though labour is cheap, there is neither the power nor the will to employ it all; because not only has the capital of the country diminished, compared with the number of labourers, but, owing to the diminished revenues of the country, the commodities which those labourers would produce are not in such request as to ensure tolerable profits to the reduced capital...

Here Malthus appears to be making a complicated argument: (a) demand for non-necessities is too low because of the end of the war, (b) attempts to export non-necessities run into a very low elasticity of demand, and (c) boosting savings by further reducing demand for non-necessities will only make things worse.

That the transition from war to peace... is a main cause of the effects observed, will be readily allowed, but not as the operation is usually explained. It is generally said that there has not been time to transfer capital from the employments where it is redundant to those where it is deficient, and thus to restore the proper equilibrium. But such a transfer could hardly require so much time as has now elapsed since the war; and I would ask, where are the under-stocked employments, which, according to this theory, ought to be numerous, and fully capable of absorbing all the redundant capital, which is confessedly glutting the markets of Europe in so many different branches of trade?... The necessary changes in the channels of trade would be effected in a year or two; but the general diminution of demand, compared with the supply occasioned by the transition from such a war to a peace, may last for a very considerable time.... If some of the principal governments concerned spent the taxes which they raised in a manner to create a greater and more certain demand for labour and commodities, particularly the former, than the present owners of them, and if this difference of expenditure be of a nature to last for some time, we cannot be surprised at the duration of the effects arising from the transition from war to peace.... When Hume and Adam Smith prophesied that a little increase of national debt beyond the then amount of it, would probably occasion bankruptcy; the main cause of their error was the very natural one, of not being able to see the vast increase of productive power to which the nation would subsequently attain. An expenditure, which would have absolutely crushed the country in 1770, might be little more than what was necessary to call forth its prodigious powers of production in 1816. But just in proportion to this power of production, and to the facility with which a vast consumption could be supplied, consistently with a rapid accumulation of capital, would be the distress felt by capitalists and labourers upon any great and sudden diminution of expenditure...

Once again, a parry to the claim that the distress of Britain's industrial working classes is merely the result of manufacturers producing too much in too narrow a range of export industries.

It is, I believe, the opinion of many persons, particularly among the mercantile classes, that nothing would so soon and so effectively increase the revenue and consumption of the country as a free issue of paper. But in holding this opinion, they have mistaken the nature of the great advantage which the national wealth may sometimes unquestionably derive from a fall in the value of the currency. The specific effect of this fall is to take away property from those who have fixed incomes, and give a greater command over the produce of the country to those who buy and sell. When the state of the national expenditure is such that there is a difficulty of supplying it... there is little doubt that the fall in the value of money, and the facility of credit which it occasioned, acting in the way described, must have contributed greatly to that rapid recovery of vast capital destroyed, which, in the same degree, never probably occurred in the history of any nation before. But, if we were now to make similar issues of paper, the effect would be very different. Perhaps a sudden increase of currency and a new facility of borrowing might under any circumstances, give a temporary stimulus to trade, but it would only be temporary. Without a large expenditure on the part of the government, and a frequent conversion of capital into revenue, the great powers of production acquired by the capitalists, operating upon the diminished power of purchasing possessed by the owners of fixed incomes, could not fail to occasion a still greater glut of commodities than is felt at present.... [I]t is of the utmost importance to recollect that, at the end of the war, the prices failed before the contraction of the currency began. It was, in fact, the failure of the prices of agricultural produce, which destroyed the country banks, and shewed us the frail foundations on which the excess of our paper-currency rested. This sudden contraction no doubt aggravated very greatly the distresses of the merchants and of the country; and for this very reason we should use our utmost endeavours to avoid such an event in future; not, however, by vain efforts to keep up prices by forcible issues of paper, in defiance at once of the laws of justice and the great principles of supply and demand, but by the only effectual way, that of steadily maintaining our paper of the same value with the coin which it professes to represent, and subjecting it to no other fluctuations than those which belong to the precious metals...

Here Malthus gets positively Austrian: the problem is that the end of the war has diminished demand for non-necessities. A monetary expansion would provide only a temporary fix--and create worse trouble in the future.