Step 1: Understanding the Concept:
The query seeks the primary criticism of Thomas Malthus's population theory from Liberal and Marxist perspectives. Malthus posited that population expands geometrically while food supply increases arithmetically, inevitably leading to poverty and famine when population surpasses resource availability.
Step 2: Detailed Explanation:
(A) Disregard for poverty as a social issue: This constitutes the central criticism. Both Liberal and Marxist schools of thought contend that poverty is not an inherent problem stemming from population expansion but a societal issue arising from inequitable resource distribution. Marx, notably, argued that capitalism inherently generates poverty and inequality, irrespective of population size. Malthus was criticized for attributing the poor's circumstances to themselves rather than the prevailing economic structure.
(B) Exclusive focus on positive and preventive checks: This is a description of his theory, not a critique. Malthus did indeed address these checks.
(C) Absence of a detailed demographic transition theory: The theory of demographic transition emerged much later, making it anachronistic to fault Malthus for not elaborating on it.
(D) Failure to theorize population explosion: Conversely, his theory represents one of the earliest frameworks for understanding population explosion, outlining rapid population growth in the absence of checks.
Step 3: Final Answer:
The fundamental criticism from both Liberal and Marxist standpoints is that Malthus erroneously framed poverty as a natural consequence of population growth, thereby overlooking its socio-economic origins in wealth disparity.