"Obscurity. . . is painful to the mind as well as to the eye; but to bring light from obscurity, by whatever labour, must needs be delightful and rejoicing."
Hume states here that the human mind dislikes confusion. If its ability to accurately perceive is hindered, the mind will intently pursue the clearance of that obstacle. The resulting illumination is pure bliss to the mind. In physical processes such as sight, this system is also applicable.
"All the colours of poetry, however splendid, can never paint natural objects in such a manner as to make the description be taken for a real landscape. The most lively thought is still inferior to the dullest sensation."
Hume postures that experiencing something with the physical senses will always be superior than experiencing the same thing vicariously through description. What this means is that what the brain creates is inferior to what exists materially. The mind cannot rival the material. Although Hume credits the beauty and skill of poetry, he considers it to be vain.
"Every effect is a distinct event from its cause. It could not. . . be discovered in the cause, and the first invention or conception of it, a priori, must be entirely arbitrary."
Hume argues that one cannot work forward from a cause to predict its effect. The cause exists separately from its effect. In other words, the cause would exist even if there were no effect resulting from itself. "A priori" is a Latin term for a line of philosophical thinking which addresses necessary conclusions from a premise. In this context, Hume says that any connection between a cause and its effect could be severed because of their completely distinct existence, so the necessary conclusion is that cause and effect are arbitrarily joined.
"Nature will always maintain her rights, and prevail in the end over any abstract reasoning whatsoever."
The forces of nature will continue without man's understanding of them. Hume believes that whether a man correctly or incorrectly identifies the system of a function of physical nature that system will continue to exist. Nature doesn't need permission to do what it does. To the furthest extent of the argument, then, man cannot control nature.
"It is impossible for us to think of anything, which we have not antecedentally felt, either by our external or internal senses."
Hume traces all epistemology, or source of knowledge, to experience. In this quotation, he asserts that all thought is the product of an experience, whether physically or mentally. If physically, then one can only think about an apple after having interacted with it using one of the five senses. If mentally, then each thought can only exist if a previous thought dealt with the aspects of that same thought. For example, to think about thinking one must first have experienced a thought.
