Thomas Malthus was an English economist and demographer who lived from 1766 to 1834. He is best known for his influential work, "An Essay on the Principle of Population," which was first published in 1798.

Malthus argued that population growth would eventually outstrip the available resources, leading to poverty, famine, and disease. He believed that population growth would increase geometrically (exponentially), while the growth of resources would only increase arithmetically (linearly). This meant that, in the long run, population growth would inevitably lead to a scarcity of resources and a decline in living standards.

Malthus's work was controversial and was often criticized for its pessimistic outlook on human progress. However, it was also influential and helped to shape the field of demography and population studies.

James Bonar was a Scottish economist and historian who lived from 1852 to 1941. He wrote extensively on the history of economic thought and was particularly interested in the work of Malthus.

Bonar's most important contribution to the study of Malthus was his biographical work, "Malthus and His Work," which was first published in 1885. This book provides a detailed analysis of Malthus's life and work, as well as an assessment of his contributions to economic thought.

Bonar argues that Malthus's work was important because it challenged the prevailing optimistic view of human progress and brought attention to the issue of population growth. He also suggests that Malthus's ideas were misinterpreted by many of his contemporaries, who saw his work as a call for population control or as an attack on the poor.

Overall, Bonar's work on Malthus helped to shed light on the importance of Malthus's contributions to economic thought and the continuing relevance of his ideas in modern times.