# Of the Idea of Necessary Connection explained — An Enquiry Concerning Human Understanding > Chapter companion for An Enquiry Concerning Human Understanding by David Hume. ## What happens Hume examines the origin of the idea of necessary connection, arguing that it cannot be derived from any single instance of cause and effect, but arises from the mind's habitual transition after repeated experiences of constant conjunction. He concludes that we have no impression of power or connection in objects themselves, only a felt determination in the imagination. ## Themes in this chapter ### Causation and Necessary Connection Hume argues that the idea of necessary connection arises not from objects but from the mind's habit after repeated constant conjunction. ### Custom and Habit as Guides Custom and habit are identified as the source of the inference from cause to effect, shaping our belief in necessary connection. ## Character check-ins ### Narrator The narrator guides the inquiry into the idea of necessary connection, reflecting on the limits of human understanding. ## Key lines > Similar objects are always conjoined with similar. Of this we have experience. Suitably to this experience, therefore, we may define a cause to be an object, followed by another, and where all the objects similar to the first are followed by objects similar to the second. We observe that like objects are constantly paired with like effects, so we define a cause as something that is always followed by a particular effect, based on past experience. _Hume offers a definition of cause grounded in observed constant conjunction._ > But when many uniform instances appear, and the same object is always followed by the same event; we then begin to entertain the notion of cause and connection. We then feel a new sentiment or impression, to wit, a customary connection in the thought or imagination between one object and its usual attendant; and this sentiment is the original of that idea which we seek for. After many repeated pairings of the same cause and effect, the mind develops a habit of expecting the effect upon seeing the cause, and this habitual feeling is the true source of our idea of necessary connection. _Hume identifies the impression of custom as the origin of the idea of necessary connection._ > All events seem entirely loose and separate. One event follows another; but we never can observe any tie between them. They seem conjoined, but never connected. Events appear to be independent and unlinked; we see one after another, but never perceive any actual bond uniting them. _Hume emphasizes that we only observe succession, not any real connection between causes and effects._ ## Links - HTML: https://www.betterreads.online/discover/an_enquiry_concerning_human_understanding_se/chapters/vii-of-the-idea-of-necessary-connection - Book: https://www.betterreads.online/discover/an_enquiry_concerning_human_understanding_se - All chapters: https://www.betterreads.online/discover/an_enquiry_concerning_human_understanding_se/chapters