0.2 The State of Research

to the person who assents to it for the assent to be warranted: an argument that depends on trust in the gods has to presuppose that the gods could adequately justify the respective conclusion. Truthmaker-specific principles fulfil this requirement because they contain a specification that is relevant to the conclusion and enable the user of the argument to trace back the causal link between the truthmakers in the argument to the ultimate justification of immediate perception.

I conclude chapter 4 by pointing out that proof is the only correct standard for persuasion for the Stoics, which leads to some implausible consequences in everyday argumentative practice due to the revelation requirement.

The answers to my main questions are as follows: a sign must stand in a necessary relation to that which it signifies. The modal relation ensures that the signified can be assented to infallibly, which is necessary for katalêpsis. But the preservation of katalêpsis has the further requirement that the justification for the connection between the sign and the signified be specific to that which makes those propositions true.

After the main investigation is finished, I address open questions about divination and divinatory signs in an appendix.

0.2 The State of Research

My five central reports ( SE PH 2.104‒106, SE M 8.245‒256, SE PH 2.134‒143, SE M 8.300‒314, SE M 8.411‒423) have given rise to two different types of question in previous scholarship. One can compare these texts and wonder if they represent a historical development, or one can attempt to explicate the contents of the definitions. This study only addresses the second kind of question at length because I am primarily interested in the philosophical content of the theory of sign and proof.

There is, however, a certain tendency in scholarship, especially after Jacques Brunschwig’s influential paper ‘Proof Defined’, to compare these reports for their differences, explain the differences through different stages in the development of Stoic logic, and then to try to ascribe those stages to different groups or authors. The main representatives of this type of project are Brunschwig (1980), Ebert (1991) and Allen (2001).6 But it seems rather implausible to approach these texts in this way. For, first, this would mean that Sextus, writing in the second century AD, compared different Stoic ( or pre-Stoic) texts that were then between 300

6 Ebert gives the most thorough treatment in this area. His aim is to show that many of the logical reports in Sextus Empiricus are actually pre-Stoic and originated with the so-called Dialectical school, e. g. Philo and Diodorus. He further tries to show that the Stoic logical reports in Sextus are early Stoic and heavily influenced by the earlier Dialectical doctrines. In most cases, this project will not be relevant.

and 500 years old and chose to insert bits of those different theories into his treatment. This insertion of random bits of different doctrines would be entirely unmotivated and without any payoff as his critique stays the same in all the texts. Second, it would also mean that Sextus Empiricus is an absolutely faithful reporter. For only then could one infer from differences in his text to differences in the original sources. This would in turn presuppose that Sextus cares enough about the reports to reproduce them exactly. However, his project is to construct arguments for and against philosophical theses, not to write a history of philosophy. The reports need not be faithful to every detail to achieve that goal.

Finally, there is good reason to assume that differences in Sextus’ reports, especially between texts from PH 2 and M 8, are due to his treatment of his sources: Janáček (1950, pp. 159–161) found, when he compared the books PH 2‒3 with M 7‒11 which cover the same topics ( logic, then physics, then ethics ), that the quotations of the dogmatists are changed, according to a uniform style, between those two bodies of texts. The fact that essentially the same quotation can occur in several places with different formulations means that Sextus does not hesitate to change a quotation. Hence, everything he reports is suspect of having been tampered with by him. For if his quotations change according to their location in his works, he does not respect his opponents ’ intellectual property enough to quote them properly at all.7

In principle, of course, any reconstruction from Sextus’ reports is thus in danger of being distorted. But, on the other hand, all those different reports do exhibit substantial similarities on which I can rely to reconstruct something that resembles the Stoic theory of sign and proof as closely as possible.

The interest of previous scholarship with regard to the philosophical content of the theory has focused on the question whether the Stoics favour rationalist modes of reasoning or also include empiricist modes of reasoning in their theory. This amounts to the question whether the Stoics only recognise signs that stand in conceptual relations to that which they signify or also observable relations.

First of all, there have been several contributions in recent scholarship dedicated specifically to the question whether there are true Stoic conditionals that express empirical relations. The starting point for the recent debate is found in Frede (1974a) who argues that no empirical relation can be expressed in a true conditional. His argument concerns the Stoic demand that divinatory predictions not be phrased as conditionals but as the negations of conjunctions. Frede maintains that negations of conjunctions, being truth-functional, are only adequate for the expression of relations that are observed to hold between two events and which lack any stronger conceptual link. Thus, the stronger Stoic conditional is supposed to be reserved for these conceptual relations. He is followed in this by

7 This paragraph is inspired by Barnes (1993), a review of Ebert (1991).

Sedley (1982) who, though he deals with sign-conditionals, makes an argument about Stoic conditionals in general. Sedley approaches this topic from the contrast between Epicurean and Stoic views on signs and conditionals and adduces evidence from a work by Philodemus to show that the Stoics countenanced only true conditionals that express analytic truths.8 I critically engage with these arguments in section 1.3.1. Frede’ s view is opposed by Sorabji (1980) and Castagnoli (2004); (2009). Sorabji tends towards the possibility of true Stoic conditionals that express empirical regularities, while Castagnoli is firmly committed to the claim that the Stoics countenance such conditionals. Bobzien (1999) ascribes the view that true Stoic conditionals can express empirical relations at least to some Stoics. I agree with these latter authors and argue for such a view in section 1.3.2.9

The discussion of conditionals and sign-conditionals has been somewhat complicated by the apparent endorsement of the material conditional in the Stoic definition of the sign, which I question in section 1.1.2. But there is a line of contributions which presupposes Frede’ s view of Stoic conditionals and explains the endorsement of the material conditional for signs in such a way that there are two types of sign-conditional. This kind of interpretation is found in Brunschwig (1980), Ebert (1991) and Allen (2001) as well as in Burnyeat (1982).10 One type expresses conceptual relations and the other one empirical relations. The definition given at PH 2.104 is then supposed to employ the material conditional because that is the more general and weaker account that can be refined into the stronger Stoic account for some sign-conditionals, which is explicit in Burnyeat’ s and Allen’s treatments. Regarding the question of empiricism and rationalism, their view is thus that the Stoics accepted both empiricist and rationalist modes of reasoning as expressible through sign-relations, but that these correspond to two different types of sign-relation. Chapter 1 presents my alternative reading of the definition of the sign according to which that definition presupposes the stronger Stoic account throughout, and that account accommodates empirical relations.

This line of interpretation, which stems from Brunschwig, also has an impact on the definition of proof. Specifically, it appears in Brunschwig’s diagnosis of the dichotomy, within the reports on proof in Sextus Empiricus, between arguments that are revelatory, and hence proofs, and those that are merely progressive. On this interpretation, this difference is due to the kind of sign and sign-

8 Gourinat (2000) and Allen (2001) also restrict Stoic conditionals to conceptual relations. LaBarge (2002) and Schallenberg (2008) suggest that the Stoics do accept conditionals that express empirical relations under the label ‘conceptual necessity’ . 9 Discussions of whether conditionals should be understood in rationalist or empiricist terms can also be found in: Brochard (1892), Hamelin (1908), Bréhier (1908), Gould (1967), Verbeke (1978). 10 See also Gourinat (2000) and Tuominen (2007).