It is here that the causal realist will appeal to the other two interpretive tools, viz. Note that he still applies the appellation "just" to them despite their appeal to the extraneous, and in the Treatise, he calls them "precise." Rather, they are unsatisfying. Attempting to establish primacy between the definitions implies that they are somehow the bottom line for Hume on causation. The more common Humean reduction, then, adds a projectivist twist by somehow reducing causation to constant conjunction plus the internal impression of necessity. The greatest common divisor of the two given numbers, we claim, is the distance from the starting point to the closest point of self-intersection, divided by . 24. The greatest common divisor is 3. Dividing through by 3, we get 3 and 8, the numbers used in the example above. The attempted justification of causal inference would lead to the vicious regress explained above in lieu of finding a proper grounding. The family of interpretations that have Hume’s ultimate position as that of a causal skeptic therefore maintain that we have no knowledge of inductive causal claims, as they would necessarily lack proper justification. They must have gotten some underwear at some point in their lives.

We cannot claim direct experience of predictions or of general laws, but knowledge of them must still be classified as matters of fact, since both they and their negations remain conceivable. In fact, Hume must reject this inference, since he does not believe a resemblance thesis between perceptions and external objects can ever be philosophically established. In fact, the title of Section 1.3.2 is "Of probability; and of the idea of cause and effect". In fact, it's very very difficult. We can either have a Cartesian clear and distinct idea, or we can have a supposition, that is, a vague, incomplete, what is billiards or "relative" notion. While it may be true that Hume is trying to explicate the content of the idea of causation by tracing its constituent impressions, this does not guarantee that there is a coherent idea, especially when Hume makes occasional claims that we have no idea of power, and so forth.

For instance, the Copy Principle, fundamental to his work, has causal implications, and Hume relies on inductive inference as early as T 1.1.1.8; SBN 4. Hume consistently relies on analogical reasoning in the Dialogues Concerning Natural Religion even after Philo grants that the necessity of causation is provided by custom, and the experimental method used to support the "science of man" so vital to Hume’s Treatise clearly demands the reliability of causal inference. T 1.3.2.11; SBN 77) In short, a reduction to D1 ignores the mental determination component. D1 reduces causation to proximity, continuity, and constant conjunction, and D2 similarly reduces causation to proximity, continuity, and the internal mental determination that moves the first object or idea to the second. If it is true that constant conjunction (with or without the added component of mental determination) represents the totality of the content we can assign to our concept of causation, then we lose any claim to robust metaphysical necessity. However, this practice may not be as uncharitable as it appears, as many scholars see the first definition as the only component of his account relevant to metaphysics. Even considering Hume’s alternate account of definitions, where a definition is an enumeration of the constituent ideas of the definiendum, this does not change the two definitions’ reductive nature.

The suggestion is this: Simple ideas are clear and distinct (though not as vivid as their corresponding impressions) and can be combined via the various relations. The realist Hume says that there is causation beyond constant conjunction, thereby attributing him a positive ontological commitment, whereas his own skeptical arguments against speculative metaphysics rejecting parity between ideas and objects should, at best, only imply agnosticism about the existence of robust causal powers. However, the position can be rendered more plausible with the introduction of three interpretive tools whose proper utilization seems required for making a convincing realist interpretation. This book explores the projectivist strand of Hume’s thought, and how it helps clarify Hume’s position within the realism debate, presenting Hume’s causal account as a combination of projectivism and realism. Our experience of constant conjunction only provides a projectivist necessity, but a projectivist necessity does not provide any obvious form of accurate predictive power.