Descartes was suspicious of the senses and believed that it should be secondary to the intellect. He began his philosophical tradition by rejecting everything that he had learned from the senses up until that point and beginning from scratch. He thought that if he started at nothing he could bypass all of the errors that philosophers have made due from the feedback that the senses had caused the reason. He gives examples of the senses having deceived and then sees this as a reason to trust the sense’s credibility (Descartes, 1-7).
Descartes believes throughout his First Meditations on Philosophy that “pure mathematics” is of a higher degree of reasoning than the inferences of “corporeal bodies.” He believes that the answers we get from equations are answers that we know, even if nothing really corresponds to them in the physical world.
Two important terms that Descartes uses is imagination and pure intellection. Descartes wants to be clear in demonstrating the difference between these two terms. He writes, “I remark in the first place the difference that exists between the imagination and pure intellection.” Imagination takes on a familiar meaning, in that it is the mind visualizing something. Descartes uses the example of a triangle. Pure intellection, is grasping fully the concept of an object, this is why Descartes also calls this “conception.” At the level of the triangle, there is very little tangible difference between pure intellection and imagination. But with a more complicated polygon, the difference becomes noticeable. Descartes believes that when it comes to containing in the mind a chilliagon—a figure with a thousand sides—pure intellection allows a mind to grasp this concept whereas imagination reaches a limit and cannot actually conjure up a figure with exactly a thousand sides.
In the example “Don’t turn off the light! I won’t be able to see” Hume would see this as an inference based on observances of past experiences. Both causes and effects, Hume says, are governed by the same rules, “that causes and effects are discoverable, not by reason, but by experience” (Hume, 4-13). The cause of a person not being able to see when the lights are turned off is the switch being flipped. Hume would argue that this is sense knowledge learned from observing the world. He does not believe with people being born with an instinctual knowledge but believes that causes and effects—matters of fact—are learned through human observation.
Hume saw causes and effects as falling under his category of impressions, not ideas. He believed that all matters of fact are not learned “a priori” or through reasoning, but through observing. If a dog is barking because it is hungry, and a person knows this from observing that feeding the dog will cause it to stop barking, Hume does not believe that it is rationally justified to assume if a dog is barking that he is hungry—even if the same assumption has been true a thousand times in the past. Humes would say that there is not logical justification to believe that flipping a light switch will lead to a room’s light being extinguished.
David Hume Begins his Enquiry Concerning Human Understanding by claiming that the science of human nature is dealt with by philosophers in one of the two ways. The first camp of philosopher’s views man as born for action and the primary objective for a man is to attain the ends that are beneficial to him and avoid those in which are deleterious to his life and well-being. The second camp, and the one that Hume aligns himself with, believes that man is a reasonable being that desires to attain understand and cultivate his intellect.
How that intellect is cultivated is a major disagreement between Humes and Descartes. Descartes wanted a clean system, while human, with a Zen-like attitude, wanted to see the world as it was. In rejecting the notion of prior principles, Descartes thought that he could build a perfect system of thought that would not need to be rethought. Hume thought “Nature will always be regular in its operations. If there is anything in any arguments of this nature, they are surely too abstruse to be known by such imperfect understandings as those of animals” (Hume 55-9).
Hume aligns himself with this second camp; he believes that there are serious shortcomings in the way that intellects have been cultivated by previously thinkers. Indeed, he writes that there is a “general disillusionment that a philosophy has not yet been solved.” The lack of clarity in philosophy for Hume is a result of empirically formed ideas having been incorrectly categorized about their attributes.
Hume goes on to describe what can be considered his most important basis in his enquiry that has been called Hume’s fork. This is “All objects of human reason or enquiry may naturally be divided [into] Relations of Ideas and Matters of Fact.” Propositions that are discoverable by mere though and without a counterpart in the actual world fall into the category of Relations of Ideas while Matters of Fact encompass the category that includes experience. Experience causes us to be able to view objects and make conjectures through Resemblance, Continuity, and Causation. As Hume believes that “Sensible objects always [have] a greater influence on [us]” Matters of fact are made sensible through our experience of observing cause and effect. And though the case for cause and effect can appear convincing, Hume would argue against every knowing a thing through cause and effect with certainty. Indeed, he distinguished that the two statements “the sun will rise tomorrow” and “the sun will not rise tomorrow” as both neither being true or false but instead speculative and arrived at through past observation.
Descartes, Rene. "Meditations on First Philosophy." Ucon.edu. Web. 6 Nov. 2014.
Hume, Dave. "An Enquiry Concerning Human Understanding." Early Modern Text. Web. 2 Nov. 2014.