Essays, or Discourses, Vol. 4 (of 4): Selected from the Works of Feyjoo, and Translated from the Spanish

A collection of philosophical essays written in the late 18th century. The volume gathers short, argumentative pieces on natural philosophy, epistemology, and morals that challenge inherited Aristotelian doctrine and promote cautious, experiment‑based reasoning. Expect lively “paradoxes” that overturn common opinions about fire, air, water, and qualities, alongside reflections on the limits of human knowledge and the pretensions of learned display. It will appeal to readers of Enlightenment thought, history of science, and skeptical philosophy. The opening of the volume presents a table of contents and then launches into “Physical Paradoxes,” where the author argues from experiments that solar heat concentrated by burning‑glasses surpasses elemental fire, that air is naturally cold absent the sun’s influence, and that water tends toward solidity, not fluidity. He contends that so‑called “occult qualities” are no more obscure than familiar ones (magnetism versus heat), that united forces are not always stronger (citing thread and rope tests), and that variations in sunlight and warmth stem partly from sunspots; he explains why a burning‑glass works better in cold and why a flame’s cone is a forced shape due to air pressure. He then claims metals reside in plants (magnetic particles in ashes, “metallic vegetation,” and a bold conjecture linking the earth’s magnetism to ubiquitous iron), before beginning “On Sceptical Philosophy,” distinguishing prudent from extreme doubt, reappraising ancient skeptics, and defending a practical trust in “experimental” evidence against dream and delusion arguments. This opening culminates in the thesis that natural philosophy yields probability rather than demonstration, illustrating the point by showing how uncertain our definitions of species, genera, and even “man as a rational animal” remain, with doubts extending to animals’ sensation and plants’ sensitivity.