Law of Population was a treatise written  as a response to works on population growth by an English cleric and what?
Law of Population Law of Population (1830) was a massive treatise written by Michael Thomas Sadler as a response to Thomas Robert Malthus's works on population growth, notably "An Essay on the Principle of Population" (first edition 1798). In his essay, Sadler refutes Malthus' conclusions regarding the geometric growth of populations and proposes that the growth of populations is a far less worrisome menace. At this period population growth had become a "political bugbear" throughout England, much in a way comparable to modern day fears of terrorism or Cold War fears of nuclear war.
Parson-naturalist A parson-naturalist was a cleric (a "parson", strictly defined as a country priest who held the living of a parish, but the term is generally extended to other clergy), who often saw the study of natural science as an extension of his religious work. The philosophy entailed the belief that God, as the creator of all things, wanted man to understand his creations and thus to study them by collecting and classifying organisms and other natural phenomena.