Key Concepts

Argument Explanation
Empiricism Hume argues that all human knowledge is derived solely from experience and that there are no innate ideas or principles. Our ideas are either impressions (direct sensations) or copies of impressions (reflections or memories).
Critique of Causality Hume challenges the notion of causality, arguing that we cannot know with certainty that one event causes another. We only observe constant conjunction (one event following another), but we cannot perceive any necessary connection between them.
Problem of Induction Hume raises the problem of induction, which questions the validity of drawing general conclusions from particular observations. He argues that there is no rational basis for the principle of induction, which is the foundation of scientific reasoning.
Skepticism about Miracles Hume presents a skeptical argument against believing in miracles, which he defines as violations of the laws of nature. He argues that it is always more probable that the testimony about a miracle is false than that the miracle occurred.
Critique of Metaphysics Hume criticizes traditional metaphysics, arguing that many philosophical concepts, such as substance, causality, and the self, are not based on empirical evidence and are therefore meaningless or incoherent.
Bundle Theory of the Self Hume denies the existence of a unitary, enduring self or soul. Instead, he argues that the self is nothing but a bundle of perceptions (impressions and ideas) that are constantly changing and have no underlying unity.

Quotes

Chapter Quote
Chapter 1: Of the Different Species of Philosophy "There is, indeed, no greater degree of scepticism, and no more refined degree of caution than what seems requisite in all reasoning concerning matters of fact."
Chapter 2: Of the Origin of Ideas "All the perceptions of the human mind resolve themselves into two distinct kinds, which I shall call IMPRESSIONS and IDEAS."
Chapter 3: Of the Association of Ideas "It is evident, that there is a principle of connection between the different thoughts or ideas of the mind and that in their appearance to the memory or imagination, they introduce each other with a certain degree of method and regularity."
Chapter 4: Sceptical Doubts Concerning the Operations of the Understanding "When we look about us towards external objects, and consider the operations of causes, we are never able, in a single instance, to discover any power or necessary connection; any quality, which binds the effect to the cause, and renders the one an infallible consequence of the other."
Chapter 5: Sceptical Solution of These Doubts "Having thus established the validity of this inference from the impression of a sensation to the idea of the cause; or, in other words, the validity of our knowledge of the external world, we must next consider whether it amounts to what we call a necessarily certain inference, or whether it be only probably certain."
Chapter 7: Of the Idea of Necessary Connexion "But there is nothing in a number of instances, different from every single instance, which is supposed to be exactly similar; except only, that after a repetition of similar instances, the mind is carried by habit, upon the appearance of one event, to expect its usual attendant, and to believe that it will exist."
Chapter 10: Of Miracles "A wise man, therefore, proportions his belief to the evidence."
Chapter 12: Of the Academical or Sceptical Philosophy "Suppose a person, though endowed with the strongest faculties of reason and reflection, to be brought on a sudden into this world; he observes a continual succession of objects, and one event following another, but he would not be able to discover, without further experience, whether any one event was the cause of another."

Contents

Chapter Title Summary
1 Of the Different Species of Philosophy This chapter contrasts two types of philosophy: the "easy and obvious," which is related to common life and behavior, and the "accurate and abstruse," which is complex and theoretical. Hume discusses the nature and limits of each and sets the stage for his approach.
2 Of the Origin of Ideas Hume argues that all ideas are derived from sensory impressions. He distinguishes between 'ideas' (the less vivid mental representations) and 'impressions' (the more vivid sensory experiences).
3 Of the Association of Ideas Hume discusses how ideas are connected in the mind through three principles: resemblance, contiguity, and cause and effect. These principles explain how the mind transitions from one idea to another.
4 Sceptical Doubts concerning the Operations of the Understanding Hume explores doubts about human understanding, focusing on the concept of causality. He questions how we come to know cause and effect, arguing that our beliefs in causality arise from experience, not logical certainty.
5 Sceptical Solution of these Doubts Hume proposes that our belief in causality is a result of habit or custom, formed through repeated experiences of events appearing in conjunction. He emphasizes that this belief is not founded on reason but on a mental propensity.
6 Of Probability This chapter deals with human understanding of probability. Hume explains how probabilities are formed based on past experiences and the notion of chance and discusses how this influences human judgment and decision-making.
7 Of the Idea of Necessary Connection Hume delves deeper into the idea of causation, arguing that the notion of a necessary connection between causes and effects is not derived from reason or any intrinsic feature of the events but from the mind's habit of associating certain events together.
8 Of Liberty and Necessity Hume addresses the debate between free will and determinism, arguing that these concepts can be reconciled. He claims that necessity (causation) is compatible with liberty (freedom of actions) and that human actions must be understood through cause and effect.
9 Of the Reason of Animals Hume compares human reasoning to that of animals, arguing that both operate on similar principles of learning from experience, demonstrating that animals also form beliefs based on custom and habit.
10 Of Miracles Hume critically examines the credibility of miracles, arguing that they violate the laws of nature and that the evidence for them is usually insufficient to overcome the strong evidence we have for those laws. He asserts that belief in miracles is typically based on unreliable testimony.
11 Of a Particular Providence and of a Future State Hume discusses religious and metaphysical ideas about divine providence and the afterlife, expressing skepticism about claims that extend beyond empirical evidence. He asserts that such beliefs often lack rational foundation.
12 Of the Academical or Sceptical Philosophy Hume outlines the philosophical approach known as Academic Skepticism, which suspends judgment due to the uncertainty of knowledge. He defends a moderate skepticism, suggesting that while absolute certainty is unattainable, practical knowledge is still useful and achievable.