# Section II: Of Probability, and of the Idea of Cause and Effect explained — A Treatise of Human Nature > Chapter companion for A Treatise of Human Nature by David Hume. ## What happens Hume examines the nature of causation, distinguishing it from other relations like identity and time/place. He argues that causation is the only relation that allows us to infer beyond our senses, and he seeks to find the impression from which the idea of causation arises. He identifies contiguity and succession as essential but insufficient, and introduces the concept of necessary connection, which he will investigate further. ## Themes in this chapter ### Empiricism and the Primacy of Impressions Hume insists that the idea of causation must be traced to its originating impression, and he examines contiguity, succession, and necessary connection as candidates. ### Skepticism About the External World Hume argues that causation is the only relation that goes beyond the senses, yet he questions our ability to know necessary connections, leading to skeptical conclusions about our knowledge of external objects. ## Character check-ins ### David Hume The author, who systematically analyzes the idea of causation, questioning its origin and necessary connection. ## Key lines > All kinds of reasoning consist in nothing but a comparison, and a discovery of those relations, either constant or inconstant, which two or more objects bear to each other. All reasoning is just comparing objects and finding how they relate, whether consistently or not. _Hume sets the stage for his analysis of relations as the basis of reasoning._ > It is only causation, which produces such a connection, as to give us assurance from the existence or action of one object, that it was followed or preceded by any other existence or action. Only causation lets us infer from one thing's existence that another thing existed before or after it. _Hume highlights causation as the key relation for going beyond immediate experience._ > An object may be contiguous and prior to another, without being considered as its cause. There is a necessary connection to be taken into consideration; and that relation is of much greater importance, than any of the other two above-mentioned. Just because one thing is next to and before another doesn't make it the cause; we also need to consider a necessary connection, which is more important. _Hume identifies the missing element in his analysis of causation: necessary connection._ ## Links - HTML: https://www.betterreads.online/discover/a_treatise_of_human_nature_se/chapters/section-ii-of-probability-and-of-the-idea-of-cause-and-effect - Book: https://www.betterreads.online/discover/a_treatise_of_human_nature_se - All chapters: https://www.betterreads.online/discover/a_treatise_of_human_nature_se/chapters