Monday, 27 April 2015

Entia Nomina V CFP

The “Entia et Nomina” series features English language workshops for young researchers in formally oriented philosophy, in particular in logic, philosophy of science, formal epistemology or philosophy of language. The aim of the workshop is to foster cooperation among young philosophers with a formal bent from various research groups. The fourth workshop in the series was Trends in Logic XIV and took place at Ghent University in 20014The fifth workshop in the series will take place from 9 to 11 September 2015 in Krakow, Poland.

The Entia et Nomina V workshop will be preceded by the 4th workshop of The Budapest-Krakow Research Group on Probability, Causality and Determinism (

Extended abstract submission deadline: May 15, 2015.
More details and full CFP at:

The European Society for Analytic Philosophy - new webpage

By Catarina Dutilh Novaes

The European Society for Analytic Philosophy was created in 1990, with the mission to promote collaboration and exchange of ideas among philosophers working within the analytic tradition, in Europe as well as elsewhere. It has thus been responsible for organizing major conferences every 3 years, the highly successful ECAP’s.

The current Steering Committee (of which I am a member), under the leadership of current president Stephan Hartmann, is seeking to expand the ways in which we can serve the (analytic) philosophical community in Europe. We will of course continue to organize ECAP, which will take place in 2017, and for which we already have a fantastic lineup of invited speakers (check it out!). But we are also considering various ways in which we can provide valuable services to the ESAP members, such as negotiating journal access with publishers (this is still in the making), among other initiatives. In particular, the brand-new website of ESAP is now online, and the goal is, among others, to concentrate useful information for (analytic) philosophers working in Europe all in one place.

However, we are only getting started, and at this points suggestions on how ESAP can truly support and galvanize the analytic philosophy community in Europe (as well as strengthening ties with colleagues elsewhere) are much welcome! We haven’t even started with an official membership system yet, precisely because we first want to have a number of services in place so as to make membership to the ESAP an attractive proposition. What are the initiatives and services we could provide that would really make a difference and facilitate the activities of our members?  Comments with suggestions below would be much appreciated!

Thursday, 23 April 2015

Jamesian epistemology formalised: an explication of 'The Will to Believe'

Famously, William James held that there are two commandments that govern our epistemic life.
There are two ways of looking at our duty in the matter of opinion, --- ways entirely different, and yet ways about whose difference the theory of knowledge seems hitherto to have shown very little concern. We must know the truth; and we must avoid error, --- these are our first and great commandments as would be knowers; but they are not two ways of stating an identical commandment [...] Believe truth! Shun error! --- these, we see, are two materially different laws; and by choosing between them we may end by coloring differently our whole intellectual life. We may regard the chase for truth as paramount, and the avoidance of error as secondary; or we may, on the other hand, treat the avoidance of error as more imperative, and let truth take its chance. (Section VII, James 1896)
In this note, I give a formal account of James' claim using the tools of epistemic utility theory. I begin by giving the account for categorical doxastic states --- that is, full belief, full disbelief, and suspension of judgment. Then I will show how the account plays out for graded doxastic states --- that is, credences. The latter part of the note thus answers a question left open in (Pettigrew 2014). (Konek forthcoming) gives a related treatment of imprecise credences.

It is not entirely clear whether James intends, in The Will to Believe, to speak of beliefs and disbeliefs or of credences.  He certainly talks of ''options'' between ''hypotheses'', which suggests the choice between two categorical states --- belief in one hypothesis or belief in the other. But he also talks of different strengths of a ''believing tendency'' and suggests that only a hypothesis with the ''maximum of liveness'' (presumably the maximum ''believing tendency'') counts as a belief (Section I, James 1896). In any case, in this note, we treat both.

Thursday, 16 April 2015

Dynamic epistemic logic solves the birthday puzzle

Many of you will have come across the 'birthday puzzle' that went viral this week:

Proving that philosophical logicians can make real contributions to serious, societal problems, my colleague Barteld Kooi has made a video where he explains how the puzzle can be solved with the help of dynamic epistemic logic. (Barteld is one of the most prominent researchers working in the field -- in particular, he is one of the authors of Dynamic Epistemic Logic (2008) and one of the editors of the much more reasonably priced Handbook of Epistemic Logic (2015).) Here is the video:

Moreover, logician and ninja-woman Audrey Yap of University of Victoria has also provided a solution to the puzzle using similar tools, which is represented in a series of pictures; the series can be found in this post by Richard Zach.

Homework for M-Phi readers (please comment below for your answers): how are the two solutions, Barteld's and Audrey's, related? Are they similar, are they different? If different, how so? Let us know!

Friday, 10 April 2015

Aristotle's definition of the syllogism -- a dialogical interpretation

By Catarina Dutilh Novaes
(Cross-posted at NewAPPS)

(I am currently finishing a paper on the definition of the syllogism according to Aristotle, Ockham, and Buridan. I post below the section where I present a dialogical interpretation of Aristotle's definition.)

Aristotle’s definition of ‘syllogismos’ in Prior Analytics (APri) 24b18-22 is among one of the most commented-upon passages of the Aristotelian corpus, by ancient as well as (Arabic and Latin) medieval commentators. He offers very similar definitions of syllogismos in the Topics, Sophistical Refutations, and the Rhetoric, but the one in APri is the one having received most attention from commentators. In the recent Striker (2009) translation, it goes like this (emphasis added):
A ‘syllogismos’ is an argument (logos) in which, (i) certain things being posited (tethentôn), (ii) something other than what was laid down (keimenôn) (iii) results by necessity (eks anagkês sumbainei)(iv) because these things are so. By ‘because these things are so’ I mean that it results through these, and by ‘resulting through these’ I mean that no term is required from outside for the necessity to come about.
It became customary among commentators to take ‘syllogismos’ as belonging to the genus ‘logos’ (discourse, argument), and as characterized by four (sometimes five) differentiae:

(i)            there are at least two premises which are posited
(ii)          the conclusion is different from the premises
(iii)         the conclusion follows necessarily from the premises
(iv)         the premises imply the conclusion by themselves; they are jointly necessary and sufficient for the conclusion to be produced.

My starting point is the idea that the best way to understand Aristotle’s project in the APri is as the formulation of a formal theory that could be suitably applied in particular in contexts of dialectical disputations. In other words, dialectical (or more generally, dialogical) considerations are always in the background in the development of the syllogistic theory (as also argued by (Kapp 1975)). True enough, he states at the very beginning of APri that the framework applies both to demonstrative and to dialectical syllogisms. But in both cases we may think of a multi-agent, dialogical situation (e.g. demonstration in the context of teaching), even if there are important differences between dialectical and demonstrative contexts. However, while the dialectical context is inherently dialogical and multi-agent, the demonstrative context need not be.

As Aristotle presents it in Chap. 1 of Book I, the distinction between dialectical and demonstrative syllogisms seems to pertain exclusively to the status of the premises: if known to be true, and more primary than the conclusion, then the syllogism will be demonstrative; if merely ‘reputable’ (endoxa), then the syllogism is dialectical. But with respect to the pragmatics of the two situations, there are other relevant differences. In particular, demonstrative syllogisms used in the context of teaching will presuppose an asymmetric relationship between the interlocutors (teacher and pupil), whereas in a dialectical context, although questioner and answerer have different roles to play, their statuses are usually comparable – they are peers. Indeed, the overall goals of a demonstration are quite different from the goals of a dialectical disputation, even though both can rely on syllogistic as a background theory of argumentation.

Be that as it may, each of the clauses formulated by Aristotle and numbered above can be given compelling dialogical, if not dialectical, explanations (on occasion I will also refer to demonstrative contexts). Let us discuss each of them in turn.

(i) Multiple premises. This requirement excludes single-premise arguments as syllogistically correct. Indeed, in the formal theory subsequently developed in APri, the arguments considered are almost exclusively those that we now refer to as syllogistic arguments, namely composed of two premises and one conclusion, all of which are categorical sentences of the A, E, I, O forms. But as often noted, this definition excludes for example the conversion rules (from AiB infer BiA and vice-versa; from AeB infer BeA and vice-versa), creating some difficulty to account for the nature of the validity of these rules. Moreover, consider the following description of the general enterprise by Striker:
Aristotle intended his syllogistic to serve as a general theory of valid deductive argument, rather than a formal system designed for a limited class of simple propositions. (Striker 2009, 79)
If we follow Striker (as I think we should!), the specific features of the theory later developed in APri should not be taken to explain the general definition at the starting point: this would amount to putting the cart before the horse. Indeed, it is the formal theory that is meant to offer a regimented account of the conceptual starting point, which is the general notion of a valid deductive argument. So this specific feature of the formal apparatus cannot be summoned to explain this aspect of the definition.

What could then explain the requirement that there be multiple premises? As noted by Striker (2009, 79), the verb ‘to syllogize’ originally meant something like ‘to add up’, ‘to compute/calculate’, and so it immediately suggests the idea of ‘putting things together’, of a fusion of more than one element (a point often made by the ancient commentators).

Plato already used the term ‘to syllogize’ in the sense of ‘to infer’ or ‘to conclude’, which Aristotle seems to have adopted. Indeed, from a dialectical/dialogical perspective as illustrated in Plato’s dialogues, the multiple premises requirement makes good sense. In a typical dialectical situation, the questioner (e.g. Socrates) elicits a number of discourse commitments from the answerer, and then goes on to show that they are collectively incoherent – for example, because they entail something absurd – thus producing a refutation. Typically, a refutation will not come about with only one discursive commitment: it is usually the interaction of multiple commitments that gives rise to interesting (and sometimes embarrassing!) conclusions.

Notice also the use of the terms ‘posited’ and ‘laid down’, which have a distinctive dialectical flavor. They introduce the dimension of a speech-act, of an agent actually putting forward premises to an interlocutor or audience, again suggesting multi-agent situations. Later authors such as Boethius will make the multi-agent dimension even more explicit, adding that the premises are not only laid down by the producer, but also granted by the receiver.

(ii) Irreflexivity. Aristotle’s requirement that the conclusion be different from the premises seems puzzling at first sight, since it entails that the consequence relation underlying syllogistic is irreflexive. This is in tension with the currently widely accepted view that reflexivity is a core feature of deductive validity.

However, here again, taking into account the various contexts of application of syllogistic arguments, irreflexivity makes good sense for each of them (as argued in (Duncombe 2014)). Indeed, in a demonstrative context, the function of a syllogism is to lead from the known to the unknown, and so obviously premises and conclusion should be different. In a dialectical context, it makes no sense to ask the opponent to grant as a premise precisely that which one seeks to establish as a conclusion; this would amount to an instance of petition principii. So the irreflexivity of the syllogistic consequence relation is exactly what one would expect, given the applications Aristotle seems to have in mind when developing the theory. (There are issues of propositional identity that arise in connection with this requirement (e.g. are logically equivalent propositions such as AiB and BiA ‘the same’?), but we will set those aside for the present purposes.)

(iii) Necessary truth-preservation. Aristotle distinguishes syllogistic arguments from those whose premises make the conclusion likely but not certain, such as induction or analogy. It is in this sense that his main target seems to be the notion of a valid deductive argument, but from the start necessary truth-preservation will be a necessary but not sufficient condition for deductive validity (in particular, in light of the three other clauses).

There is much to be said with respect to why the ‘results by necessity’ clause makes sense in the different contexts of application of syllogistic arguments, in particular demonstrative and dialectical contexts, but let us keep it brief for the present purposes. In a dialectical context, an argument having this property will force the opponent to grant the conclusion, if she has granted the premises, so it is a strategically advantageous property for the one proposing the argument. In a demonstrative context, Aristotle’s whole theory of demonstration is premised on the idea of deriving rock-solid conclusions from self-evident axioms, and thus again necessary truth-preservation becomes advantageous.

(iv) Sufficiency and necessity of the premises. This is perhaps the most obscurely formulated of the four clauses in the definition, and indeed Aristotle goes on to offer a gloss of what he means, which is however still not very illuminating. In the Topics, his phrasing is more transparent, as described by Striker:
The definition as given in the Topics is clearer in this respect: it has the clause ‘through the things laid down’ instead of ‘because these things are so’. In this passage, Aristotle adds the remark that this clause should also be understood to mean that all premises needed to derive the conclusion have been explicitly stated. (Striker 2009, 81)
This clause has been variously interpreted by commentators. It seems to amount to some sort of relevance requirement: it must be precisely in virtue of the premises that the conclusion comes about. To be sure, the premises may be false or uncertain (at least outside demonstrative contexts), but the conclusion must be produced through them. Some commentators, in particular in the Arabic tradition, have interpreted this clause as a requirement for an essential connection between premises and conclusion. But the requirement can also be interpreted logically as stating that no premise is redundant for the conclusion to come about; all of them are de facto needed for the conclusion to result of necessity. (This is indeed one of the two main formulations of the requirement of relevance in modern relevant logics, known as ‘derivational utility’ (Read 1988, 6.4).) This requirement is also often discussed in connection with the fallacy of False Cause, which we will discuss briefly below.

Moreover, as Aristotle’s gloss suggests, this clause can also be read as the requirement that everything that is needed for the conclusion to result of necessity has been explicitly stated; there are no hidden premises required (“no term is required from outside”). And so, this clause may be read as the requirement that the premises laid down are exactly those needed for the conclusion to come about; no more, no less.

In demonstrative contexts, this clause is very natural: for Aristotle, a demonstration is an explication unearthing the causes of a given phenomenon, and so both redundancy and lack of explicitness go against this desideratum. In dialectical contexts however, both these requirements are less straightforward: the participants may have a fair amount of endoxa in common, which could plausibly be taken for granted without being explicitly put forward; and redundancy may be advantageous in purely adversarial contexts, as asking for various redundant premises may serve the strategic purpose of confusing one’s opponent. But in the Topics, Aristotle wants to move away from the purely adversarial dialectical disputes (though he also gives advice on how to perform well in such cases – see also the Sophistical Refutations) and towards a more cooperative model – dialectic as inquiry, where two parties together consider what would follow from given assumptions (Topics VIII.5). In such contexts, redundancy would be out of place, and relevance comes out as a notion related to cooperativeness.

Friday, 3 April 2015

On Quine's Arguments Against QML, Part 3: Ontology

Read part 1; read part 2.

The second objection that Quine levels against quantified modal logic in [1] is that its ontology is “curiously idealistic” and “repudiates material objects” [1, p. 43]. This consideration arises from the same starting point as the objection discussed in the previous subsection: The problem of quantifying into an intensional context

Consider the following:

(6) ∃x(x is red ∧ M(x is round))

Quine says that in order to interpret this sentence, we need supplementary criteria, and suggests one potential criterion:

(ii) An existential quantification holds if there is a constant whose substitution for the variable of quantification would render the matrix true [1, p. 46],

where a ‘matrix’ is simply “an expression which has the form of a statement but contains a free variable” [2, p. 126]. This criterion, he argues has the consequence that

there are no concrete objects (men, planets, etc.), but rather that there are only, corresponding to each supposed concrete object, a multitude of distinguishable entities (perhaps ‘individual concepts’, in Church’s phrase) [1, p. 47].

Thus, instead of having concrete objects such as Venus, Mars, and Pluto in our ontology, we have instead things such as Venus-concept, Evening-Star-concept, Morning-Star-concept, etc. Let us spell out his argument for this conclusion.

Suppose that Venus, Evening Star, and Morning Star are all constants in our language suitable for use in criterion (ii). Each of these constants bears a certain relationship to itself and to the other in virtue of the empirical data; Quine calls this relation ‘congruence’. The question is what these constants are names of; if they pick out concrete objects in the domain, then they should all pick out the same concrete object, namely, a planet. But we shall see that truths about congruence prevent us from taking as the values of these constants concrete objects.

Let C represent the relation of congruence; we have the following two truths:

(7) Morning Star C Evening Star ∧ L(Morning Star C Morning Star)

(8) Evening Star C Evening Star ∧ ¬L(Morning Star C Evening Star)

From these along with (ii), we can conclude that there are at least two distinct objects in the ontology which are congruent with ‘Evening Star’:

(9) ∃x(x C Evening Star ∧ L(x C Morning Star)

(10) ∃x(x C Evening Star ∧ ¬L(x C Morning Star)

But since there is but one planet Venus, it must be the case that the ontology is not made up of planets and other concrete objects, but rather concepts of planets, for only then could we find constants whose substitution for the variable would make (9) and (10) true.

A strange ontology this may be, but it does not immediately follow from this that QML is incoherent or that expressions involving quantification into modal contexts are nonsense. For let us recall what Quine’s modal logic is a modal logic of: Not logical necessity, not physical necessity, but analytic necessity. As discussed above, the notion of analyticity is defined in terms of synonymy. Synonymy—sameness of meaning or sameness of intension—is itself a notion concerning concepts, not objects. Therefore, in a modal logic designed to explicate a notion based on concepts rather than objects, we should not be surprised that the ontology of that logic is populated with concepts, rather than objects. What is surprising is that Quine does not apparently recognize this, despite the fact that he says, elsewhere, that “being necessarily or possibly thus and so is in general not a trait of the object concerned, but depends on the manner of referring to the object” [3, p. 148, emphasis added]. If the logic of necessity is thus not about properties of actual objects but of ways that objects are described, then we should in fact expect that the ontology of the logic to not be populated by actual objects, but rather by ways that objects can be described, i.e., by concepts.


  • [1] W. V. Quine. The problem of interpreting modal logic. Journal of Symbolic Logic, 12(2):43–48, 1947.
  • [2] Willard V. Quine. Notes on existence and necessity. Journal of Philosophy, 40(5):113–127, 1943.
  • [3] W. V. O. Quine. From a Logical Point of View. Harper & Row, 2nd edition, 1961.

© 2015 Sara L. Uckelman