Common ancestry is a central feature of the theory of evolution, yet it is not clear what “common ancestry” actually means; nor is it clear how it is related to other terms such as “the Tree of Life” and “the last universal common ancestor”. I argue these terms describe three distinct hypotheses ordered in a logical way: that there is a Tree of Life is a claim about the pattern of evolutionary history, that there is a last universal common ancestor (...) is an ontological claim about the existence of an entity of a specific kind, and that there is universal common ancestry is a claim about a causal pattern in the history of life. With these generalizations in mind, I argue that the existence of a Tree of Life entails a last universal common ancestor, which would entail universal common ancestry, but neither of the converse entailments hold. This allows us to make sense of the debates surrounding the Tree, as well as our lack of knowledge about the last universal common ancestor, while still maintaining the uncontroversial truth of universal common ancestry. (shrink)

Common ancestry is one of the pillars of Darwin’s theory of evolution. Today, the Tree of Life, which represents how all life is genealogically related, is often thought of as an essential component in the foundations of biological systematics and so therefore of evolutionary theory – and perhaps all of biology itself. It is an iconic representation in biology and even penetrates into popular culture.

Abstract : In this paper, it is argued that Leibniz’s view that necessity is grounded in the availability of a demonstration is incorrect and furthermore, can be shown to be so by using Leibniz’s own examples of infinite analyses. First, I show that modern mathematical logic makes clear that Leibniz’s "infinite analysis" view of contingency is incorrect. It is then argued that Leibniz's own examples of incommensurable lines and convergent series undermine, rather than bolster his view by providing examples of (...) necessary mathematical truths that are not demonstrable. Finally, it is argued that a more modern view on convergent series would, in certain respects, help support some claims he makes about the necessity of mathematical truths, but would still not yield a viable theory of necessity due to remaining problems with other logical, mathematical, and modal claims. (shrink)

Mind Association 2017Elliott Sober’s first book, Simplicity, defends the view that the simplicity of a theory or hypothesis is a measure of its informativeness – roughly, simpler theories require less new information to be added to them to answer relevant questions of interest. While this measure of simplicity is question-relative, it is still what you might call a global view of simplicity – simplicity means the same thing across different scientific problems and it is always an epistemic virtue. Ockham’s Razor (...) is just good scientific reasoning. Sober’s 1988 book Reconstructing the Past: Parsimony, Evolution, and Inference argues against this global conception of simplicity and replaces it with a local one. Here, in one context parsimony means one thing while in another context it may mean something different. Similarly, whether the more parsimonious hypothesis is to be preferred is also a local matter; it... (shrink)