The doctrines of aithus have been discussed threadbare by numerous thinkers and writers and more often than not have been severely criticised.
Earlier writers even used abusive language and attributed motives to him. Some of his earlier critics were often ignorant out the simple facts of his person life, which were easily verifiable, are very amusing to know that even Karl Marx.
While criticizing us very harshly, referred to him as one who "had taken the monastic vow of celibacy," though it is a well known fact that Malthus was married and had three children.
It has already been pointed out that those who condemned Malthus as well as those who praised him often based their arguments on misconceptions either because they had not read him thoroughly or because they had not understood him correctly."
One of the reasons for the popularity of Malthusian doctrine was that he had based his arguments on two ratios the geometrical and the arithmetical. In the view of many of his critics, however, this was the weakest point in his theory.
Consequently, he was heavily attacked on this score. Kenneth Smith pointed out that these ratios concerning population growth and the means of subsistence were based on a very slender foundation and were never really proved.
Malthus's conclusion that population would double in a period of twenty-five years was based on the evidence of doubtful American statistics. He had almost completely ignored the role of immigration in the North American population growth.
His arithmetical ratio concerning the growth of the means of subsistence was also unanimously rejected, though in later years it was strongly reinforced by the law of diminishing returns, a new development in economic theory.
One argument against Malthus was that he did not clearly distinguish between fecundity the physiological capacity to reproduce and fertility the actual reproductive performance measured in terms of live births although the phenomenon of differential fertility had started making its impact about that time.
The classification of checks on population growth into the two categories of preventive and positive also came in for criticism and was cited as an example of "poor classification", for the two do not form "independent categories."
Moreover, it was pointed out that Malthus had not succeeded in connecting his positive and preventive checks vice, misery and prudence with his theory.
In general, Malthus was criticised on the following points:
(1) He placed undue emphasis on the limitation of the supply of land. The agricultural revolution of the nineteenth century, which brought in its wake the system of rotation of crops, chemical fertilisers, plant and animal breeding and improvements in the quality of livestock, brought about a tremendous increase in agricultural production. The gloomy predictions of Malthus, therefore, did not come true.
(2) Malthus under-estimated the importance of industrial development, and did not take into consideration the faster and more reliable modes of transport which helped colonial empires to provide additional raw materials, an exploitable land supply and new markets for manufactured products.
(3) His religious beliefs prevented him from grasping the possibility of the widespread use of contraceptives.
Eversley has also criticised Malthus for not using the results of the 1831 census of England and does not think that Malthus has made any significant contribution to social thought.
Kingsley Davis, on the other hand, while admitting that the doctrines of Malthus were not empirically valid, emphasised that they were nevertheless theoretically significant.