Philosophy Books in Threes

This is nothing groundbreaking, but I want to call attention to the fact that three heroes of the naturalist tradition (or so I would call them), Lucretius, Spinoza, and Hume, seem to employ a more or less three-part strategy when expounding their philosophy in their major works.

Hume’s case is the most obvious, where his A Treatise of Human Nature is split into three books: one on the understanding, one on the passions, and one on ethics and justice.

The structure of Lucretius’ De Rerum Natura is similar. The work is in six books, with the first two dealing with Epicurean atomic physics, the second two dealing with human life and the mind, and the last two taking up the universe at large (including mankind’s place in it).

Lastly, there’s Spinoza’s Ethics, where the first part expounds Spinoza’s basic ontology, the second part concerning the theory of knowledge and the philosophy of mind, and parts three, four, and five dealing with moral psychology and ethics. Granted, as readers of the Ethics will note, the “second” and “third” divisions I’m suggesting would seem to blur together, but consider that Spinoza also wrote a kind of rough draft for the Ethics called the Short Treatise on God, Man, and His Well-Being, which one call tell from the title alone treats the same basic themes.

In each case, the first part for each work begins with first principles (a skeptical empiricist epistemology for Hume, materialist physics for Lucretius, and the one substance for Spinoza) and then moves on to the application of these principles in the second part (philosophical anthropology in all three thinkers)  and third part (ethics and social philosophy for Spinoza and Hume, the formation and composition of our world and emergence of society for Lucretius).

In each of these philosophers—what makes them naturalists—the principles and explanations they employ are found within nature, and they see no need to invoke supernatural agents to account for the world, understanding, or our moral nature. None of this is to say that naturalistic philosophers have a monopoly on this tripartite structure, or that there’s anything particularly naturalistic about it. But it does raise the question of influence. De Rerum Natura was rediscovered in the Renaissance and slowly but surely made its Epicurean influence felt. Hume explicitly invokes Epicurus in both An Enquiry concerning Human Understanding and Dialogues concerning Natural Religion; Spinoza does not to my recollection make explicit reference to Epicurus or Lucretius, but Spinoza in the Ethics is famously scant on mentioning his sources, and I tend to think that the Ethics has more than a few shades of Epicurean naturalism. Could Hume and Spinoza both have been emulating Lucretius? 

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Note: It’s believed that the content of the De Rerum Natura is derived from Epicurus’ long lecture series on nature, the Peri Phuseos. Since the Peri Phuseos survives only in literal fragments recovered from beneath the ash laid down by Mt. Vesuvius, and is not to my knowledge available in English, I can’t say to what degree the structure of Lucretius’ work derives from Epicurus’.