In his work, Hume distinguishes between ideas and impressions. While impressions are caused by sensory inputs and vivid mental phenomenon, ideas are the thoughts or beliefs related to these memories. Three laws of association—resemblance, contiguity, cause and effect -- come into play in determining the link between impression and idea.
He links the notion of causation to inductive reasoning. He opines that an individual reasons inductively associating constantly conjoined events. This mental act of association is termed by Hume as the concept of causation. In literature, his theory is interpreted in three ways.
In the logical positivist interpretation, the causal propositions are analyzed in terms of regularities in perception, though the view is readily rejected by the skeptical realists. They put forward the argument that the act of causation is much more than summation of succession of events. They opine that a connection is there when two events are conjoined.
Hume had the view that the individual has no way of having perceptual access to this necessary connection. Thus, the concept of skepticism comes into play. An individual is compelled to be credulous of its objective existence which is known as ergo realism. Thus, Hume reached the conclusion that there are no necessary connections, but conjunctions that are constant. He never proposes the fact that something can arise without cause. He did not believe that causation can be reduced to regularity. He was not a realist too and Simon Blackburn terms his works as quasi-realist. The explanation is that functional change in the mind is represented by causal necessity. On the basis of previous experience, few events are anticipated or predicted. The functional change has its projection in the form of causal necessity in the human mind. As such, the assessment seems to be accurate in keeping with the functionality of the human mind. How an individual cognizes is dependent on the perceptions and experiences of that person.
“David Hume.” Lectures in Philosophy. Print.