Greek and Roman Logic

In ancient philosophy, there is no discipline called “logic” in the contemporary sense of “the study of formally valid arguments.” Rather, once a subfield of philosophy comes to be called “logic,” namely in Hellenistic philosophy, the field includes (among other things) epistemology, normative epistemology, philosophy of language, the theory of truth, and what we call logic today. This entry aims to examine ancient theorizing that makes contact with the contemporary conception. Thus, we will here emphasize the theories of the “syllogism” in the Aristotelian and Stoic traditions. However, because the context in which these theories were developed and discussed were deeply epistemological in nature, we will also include references to the areas of epistemological theorizing that bear directly on theories of the syllogism, particularly concerning “demonstration.” Similarly, we will include literature that discusses the principles governing logic and the components that make up arguments, which are topics that might now fall under the headings of philosophy of logic or non-classical logic. This includes discussions of problems and paradoxes that connect to contemporary logic and which historically spurred developments of logical method. For example, there is great interest among ancient philosophers in the question of whether all statements have truth-values. Relevant themes here include future contingents, paradoxes of vagueness, and semantic paradoxes like the liar. We also include discussion of the paradoxes of the infinite for similar reasons, since solutions have introduced sophisticated tools of logical analysis and there are a range of related, modern philosophical concerns about the application of some logical principles in infinite domains. Our criterion excludes, however, many of the themes that Hellenistic philosophers consider part of logic, in particular, it excludes epistemology and metaphysical questions about truth. Ancient philosophers do not write treatises “On Logic,” where the topic would be what today counts as logic. Instead, arguments and theories that count as “logic” by our criterion are found in a wide range of texts. For the most part, our entry follows chronology, tracing ancient logic from its beginnings to Late Antiquity. However, some themes are discussed in several eras of ancient logic; ancient logicians engage closely with each other’s views. Accordingly, relevant publications address several authors and periods in conjunction. These contributions are listed in three thematic sections at the end of our entry

'What the Tortoise said to Achilles': Lewis Carroll's Paradox of Inference

Lewis Carroll’s 1895 paper, 'What the Tortoise Said to Achilles' is widely regarded as a classic text in the philosophy of logic. This special issue of 'The Carrollian' publishes five newly commissioned articles by experts in the field. The original paper is reproduced, together with contemporary correspondence relating to the paper and an extensive bibliography

Modal Ω-Logic: Automata, Neo-Logicism, and Set-Theoretic Realism

This essay examines the philosophical significance of $\Omega$-logic in Zermelo-Fraenkel set theory with choice (ZFC). The duality between coalgebra and algebra permits Boolean-valued algebraic models of ZFC to be interpreted as coalgebras. The modal profile of $\Omega$-logical validity can then be countenanced within a coalgebraic logic, and $\Omega$-logical validity can be defined via deterministic automata. I argue that the philosophical significance of the foregoing is two-fold. First, because the epistemic and modal profiles of $\Omega$-logical validity correspond to those of second-order logical consequence, $\Omega$-logical validity is genuinely logical, and thus vindicates a neo-logicist conception of mathematical truth in the set-theoretic multiverse. Second, the foregoing provides a modal-computational account of the interpretation of mathematical vocabulary, adducing in favor of a realist conception of the cumulative hierarchy of sets

Kantian Philosophy and ‘Linguistic Kantianism’

The expression “linguistic Kantianism” is widely used to refer to ideas about thought and cognition being determined by language — a conception characteristic of 20th century analytic philosophy. In this article, I conduct a comparative analysis of Kant’s philosophy and views falling under the umbrella expression “linguistic Kantianism.” First, I show that “linguistic Kantianism” usually presupposes a relativistic conception that is alien to Kant’s philosophy. Second, I analyse Kant’s treatment of linguistic determinism and the place of his ideas in the 18th century intellectual milieu and provide an overview of relevant contemporary literature. Third, I show that authentic Kantianism and “linguistic Kantianism” belong to two different types of transcendentalism, to which I respectively refer as the “transcendentalism of the subject” and the “transcendentalism of the medium.” The transcendentalism of the subject assigns a central role to the faculties of the cognising subject. The transcendentalism of the medium assigns the role of an “active” element neither to the external world nor to the faculties of the cognising subject, but to something in between — language, in the case of “linguistic Kantianism.” I conclude that the expression “linguistic Kantianism” can be misleading when it comes to the origins of this theory. It would be more appropriate to refer to this theory by the expression “linguistic transcendentalism,” thus avoiding an incorrect reference to Kant

A point on fixpoints in posets

Let $(X,\le)$ be a {\em non-empty strictly inductive poset}, that is, a non-empty partially ordered set such that every non-empty chain $Y$ has a least upper bound lub$(Y)\in X$, a chain being a subset of $X$ totally ordered by $\le$. We are interested in sufficient conditions such that, given an element $a_0\in X$ and a function f:X\a X, there is some ordinal $k$ such that $a_{k+1}=a_k$, where $a\_k$ is the transfinite sequence of iterates of $f$ starting from $a_0$ (implying that $a_k$ is a fixpoint of $f$): \begin{itemize}\itemsep=0mm \item $a_{k+1}=f(a_k)$ \item a_l=\lub\{a_k\mid k \textless{} l\} if $l$ is a limit ordinal, i.e. $l=lub(l)$ \end{itemize} This note summarizes known results about this problem and provides a slight generalization of some of them

On Constructive Axiomatic Method

In this last version of the paper one may find a critical overview of some recent philosophical literature on Axiomatic Method and Genetic Method.Comment: 25 pages, no figure