It is commonly held that Darwin discovered natural selection in a flash of insight after reading Thomas Robert Malthus’ Essay on Population in September 1838. Additionally, most people think this was the missing piece that completed his theory of evolution. However, the Eureka moment is a myth, as is the claim that its purported insight finalized his theoretical understanding. Darwin not only slowly worked out his idea of natural selection over many months but he also took another twenty years to formulate the theory presented in On the Origin of Species. Most notably, his thinking changed radically in 1856 with the introduction of the principle of divergence. Analyzing this history demonstrates that there are a variety of misunderstandings about what exactly Darwin’s theory was, how it was structured, and whether it changed over time. Overall, this casts doubt on the claim that Darwin’s theory was ever “essentially complete,” even after contemplating several different meanings for this phrase. Rejecting this myth yields a richer understanding of the way scientific inquiry operates, especially how its methods and outcomes are justified, while augmenting our confidence in the importance of natural selection for explaining adaptive evolution.

Experience is the cornerstone of Epicurean philosophy and nowhere is this more apparent than in the Epicurean views about the nature, formation, and application of concepts. ‘The Epicureans on Preconceptions and Other Concepts’ by Gábor Betegh and Voula Tsouna aims to piece together the approach to concepts suggested by Epicurus and his early associates, trace its historical development over a period of approximately five centuries, compare it with competing views, and highlight the philosophical value of the Epicurean account on that subject. It is not clear whether, properly speaking, the Epicureans can be claimed to have a theory about concepts. However, an in-depth discussion of the relevant questions will show that the Epicureans advance a coherent if elliptical explanation of the nature and formation of concepts and of their epistemological and ethical role. Also, the chapter establishes that, although the core of the Epicurean account remains fundamentally unaffected, there are shifts of emphasis and new developments marking the passage from one generation of Epicureans to another and from one era to the next.

This chapter generalizes the ideas given in the previous chapter. It sets out the notion of a model based on a set of theories. One of these theories is the logic itself. It is, so to speak, the correct theory of theories. It correctly states the principles under which all the theories (including itself) are closed. But each theory has associated with it a closure operator. Some of these operators get the principles of theory closure quite wrong in the sense that they do not apply correctly to every theory in the model. The interaction between these closure operators can be altered in various ways, giving rise to different logical systems. The resulting formal semantics can be represented in the manner of Kit Fine’s “Models for Entailment”.