Hume’s view on knowledge is divided into two categories: ideas and facts. He emphasizes that knowledge derived from facts is not logically related and cannot be proven deductively. According to Hume, all knowledge related to facts is obtained through the senses, as there are no innate ideas to serve as a foundation(Hume, 1751, 1902, 1907).
Hume’s skepticism extends to causation, which he views as constant conjunction. He challenges the justification for inductive reasoning, asserting that past regularities do not necessarily guarantee future outcomes(Beebee, 2006). Hume contends that inductive practices are based on habit and instinct rather than reason, highlighting the lack of a solid foundation for justifying the extrapolation from past experiences to future events(Millican, 2002).
His main concern with induction lies in the potential for false conclusions, even with a large number of observations, as demonstrated by the example of the mistaken belief that all swans were white until black swans were discovered in Australia(Millican, 2002; Taleb, 2007).
According to Hume, human perceptions can be categorized into two main types: impressions and ideas. Impressions are direct and vivid perceptions that arise from our senses and emotions, while ideas are fainter copies of these impressions. Hume argued that all our thoughts and knowledge are ultimately derived from these impressions(Hume, 1751, 1902, 1907).
Regarding the use of these perceptions, Hume emphasized the process of association of ideas. He proposed that the human mind has a natural tendency to associate ideas based on certain principles, such as resemblance, contiguity, and cause and effect. These principles govern how our thoughts and perceptions are connected. For example, if we see one billiard ball striking another, our mind associates the idea of the first ball with the idea of the second ball moving(Hume, 1902; Legg & Franklin, 2017; Owen, 1993).
Of the many pages I read on Hume, this case was one of the most interesting.
“Suppose a person, though endowed with the strongest faculties of reason and reflection, to be brought on a sudden into this world; he would, indeed, immediately observe a continual succession of objects, and one event following another; but he would not be able to discover anything farther. He would not, at first, by any reasoning, be able to reach the idea of cause and effect; since the particular powers, by which all natural operations are performed, never appear to the senses; nor is it reasonable to conclude, merely because one event, in one instance, precedes another, that therefore the one is the cause, the other the effect. Their conjunction may be arbitrary and casual. There may be no reason to infer the existence of one from the appearance of the other. And in a word, such a person, without more experience, could never employ his conjecture or reasoning concerning any matter of fact, or be assured of anything beyond what was immediately present to his memory and senses.
Suppose, again, that he has acquired more experience, and has lived so long in the world as to have observed familiar objects or events to be constantly conjoined together; what is the consequence of this experience? He immediately infers the existence of one object from the appearance of the other. Yet he has not, by all his experience, acquired any idea or knowledge of the secret power by which the one object produces the other; nor is it by any process of reasoning, he is engaged to draw this inference. But still he finds himself determined to draw it: and though he should be convinced that his understanding has no part in the operation, he would nevertheless continue in the same course of thinking. There is some other principle which determines him to form such a conclusion.”
We cannot think about what we do not know. What we think we know may be an idea or an impression based on experience. Our experiences are limited and so is our knowledge and understanding. Past experiences may or may not inform the future especially when we are in doubt on the nature of the causes and the effects.