Dear Cheerful Logicians and Friends of Logic, We have a bountiful week ahead! There are four logic talks; including TWO(!) official supergroup talks.
In order here are the talks this week: All times are GMT-5. - On Tuesday at 10:00 GMT-5, Damian Szmuc will speak in the Seminario de Lógica Iberoamericana on a very apt topic for these times---*Immune* logics! - On Thursday at 14:00 GMT-5, Brendan Fong will speak in the Lógicos em Quarentena seminar on compositional perspectives on supervised learning. - Later on Thursday is the first of our official supergroup talks. At 19:00 GMT-5, Graham Priest will speak in the Melbourne Logic Seminar about Impossible Worlds. - Finally, on Friday at 11:00 GMT-5, Stephen Read will talk to us about Paul of Venice's solutions to logical paradoxes. Details are below. Worth noting is that the Thursday talk is happening an hour earlier than usual. Supergroup Talk 1: Speaker: Graham Priest (CUNY) Title: Mission Impossible Time and Date: Thursday August 13th, 19:00 GMT-5 Link: <https://ksu.zoom.us/j/7613620942> https://unimelb.zoom.us/j/846890369?pwd=TktZYmlIUGlYOU9ZaXFJcCt0TFJFZz09 Abstract: Saul Kripke's work on the semantics of non-normal modal logics introduced the idea of non-normal worlds, worlds where logically impossible things may hold. Such worlds can naturally be thought of as impossible worlds. Since Kripke's invention, the notion of an impossible world has undergone much fruitful development and application. Impossible worlds may be of different kinds—or maybe different degrees of impossibility; and these worlds have found application in many areas where hyperintensionality appears to play a significant role: intentional mental states, counterfactuals, meaning, property theory, to name but a few areas. But what, exactly, is an impossible world? How is it best to characterise the notion? To date, the notion is used more by example than by definition. In this paper I will investigate the question and propose a general characterisation, suitable for all standard purposes and tastes. In particular, it can be deployed whatever one takes the correct logic to be. Supergroup Talk 2: Speaker: Stephen Read (St. Andrews) Title: “Everything true will be false”: Paul of Venice’s two solutions to the logical paradoxes Time and Date: Friday August 14th, 11:00 GMT-5 *Link:* https://ksu.zoom.us/j/96831198878?pwd=ZnZTVmhFQjdIYUJJUXlXbkxkaUZodz09 *Meeting ID:* 968 3119 8878 *Passcode:* OfVenice Abstract: In his *Quadratura*, Paul of Venice (1369-1429) considers a sophism involving time and tense which appears to show that there is a valid inference which is also invalid. His argument runs as follows: consider the inference concerning some proposition *A*: *A* will signify only that everything true will be false, so *A* will be false. Call this inference *B*. Then *B* is valid because the opposite of its conclusion is incompatible with its premise. In accordance with the standard medieval doctrine of ampliation, Paul takes *A* to be equivalent to ‘Everything that is or will be true will be false’. But he proceeds to argue that it is possible that *B*’s premise (‘*A* will signify only that everything true will be false’) could be true and its conclusion false, so *B* is not only valid but also invalid. Thus *A* is the basis of a logical paradox, *aka* an insoluble. In his *Logica Parva*, a self-confessedly elementary texts aimed at students and not necessarily representing his own view, and in the *Quadratura*, Paul follows the solution found in the *Logica Oxoniensis*, which posits an implicit assertion of its own truth in insolubles like *B*. However, in the treatise on insolubles in his *Logica Magna*, Paul develops and endorses Roger Swyneshed’s solution, which stood out against this “multiple-meanings” approach in offering a solution that took insolubles at face value, meaning no more than is explicit in what they say. On this account, insolubles imply their own falsity, and that is why, in so falsifying themselves, they are false. We consider how both types of solution apply to *B* and how they complement each other. On both, *B* is valid. But on one (following Swyneshed), *B* has true premises and false conclusion, and contradictories can be false together; on the other (following the *Logica Oxoniensis*), the counterexample is rejected. Talks by Member Groups: *Seminario de Lógica Iberoamericana:* Speaker: Damian Szmuc (Buenos Aires) Title: Immune Logics Time and Date: Tuesday, August 11 10:00am GMT-5 Link: https://us02web.zoom.us/j/89354138458?pwd=eXRmQmltS0xnTzE4anB5Q0hWTGF2Zz09 *Meeting ID:* 893 5413 8458 *Password*: 195576 Abstract: In the past few years, the family of many-valued logics called *infectious logics* received an increasing amount of attention. These systems count with a truth-value that is assigned to a complex formula whenever it is assigned to some of its components---thus, behaving in an infectious way. Rather informally, we could say that these values behave in a "value-in-value-out" fashion. From a mathematical point of view, infectious values of this sort can be thought of as all-purpose zero elements. The aim of this talk is to discuss a family of many-valued logics that can perhaps be considered as *duals* to the infectious systems---whence, they will be called *immune logics*. In this vein, these logics count with a truth-value that is never assigned to a complex formula whenever it is assigned to some of its components, except in certain cases. Once again rather informally, we could say that in some of these cases these values behave in a "value-in-different-value-out" manner. Therefore, immune values of this sort can be thought of as all-purpose identity elements. As regards immune logics, our goal is to describe and analyze various three-valued systems. For this purpose, we explore immune logics where validity is defined by letting the immune value be designated, systems where it is undesignated, and systems where mixed notions of validity are adopted. In doing so, we highlight the links to various logics that have already appeared in the literature and some which were not discussed until now. *Lógicos em Quarentena* Speaker: Brendan Fong (MIT) Title: Backprop as Functor: A compositional perspective on supervised learning Time and Date: Thursday, August 6 14:00 GMT-5 Link: https://meet.google.com/qhk-kstn-ahy Abstract: A supervised learning algorithm searches over a set of functions A→B parametrised by a space P to find the best approximation to some ideal function f:A→B. It does this by taking examples (a,f(a))∈A×B, and updating the parameter according to some rule. We define a category where these update rules may be composed, and show that gradient descent---with respect to a fixed step size and an error function satisfying a certain property---defines a monoidal functor from a category of parametrised functions to this category of update rules. This provides a structural perspective on backpropagation, as well as a broad generalisation of neural networks. Other Notes and Announcements: - The supergroup finally has its own official website! Woohoo! Here's a link <https://sites.google.com/view/logicsupergroup/the-logic-supergroup>. Thanks to Damian Szmuc for getting this up and running! - Universität Regensburg is hosting a virtual workshop on August 27 and 28. The workshop is title *"If ifs and ands were pots and pans ..." Qualitative and quantitative approaches to reasoning and conditionals. *For more information visit this link <https://www.uni-regensburg.de/philosophie-kunst-geschichte-gesellschaft/theoretische-philosophie/workshops/2020/index.html> . - *The Logic Supergroup has a YouTube channel!* Recordings of almost all talks are available at https://www.youtube.com/channel/UCqOAS8SHP-5nGjYEE2FE6xw - To access the supergroup calendar, please follow this link: https://calendar.google.com/calendar?cid=ZGhoanNoanF1bGhmaG9xam5scDJlc2o0bDhAZ3JvdXAuY2FsZW5kYXIuZ29vZ2xlLmNvbQ - To access the member groups joint calendar, please follow this link: https://calendar.google.com/calendar?cid=aG8wNWljaGxkNXI2N2oyMnZvY3BzdmRoMWNAZ3JvdXAuY2FsZW5kYXIuZ29vZ2xlLmNvbQ - If you represent a member group and would like your events to appear on the joint calendar, be sure to add them! Contact any of the organizers if you need permission to do so. Yay for logic! -- Você está recebendo esta mensagem porque se inscreveu no grupo "LOGICA-L" dos Grupos do Google. Para cancelar inscrição nesse grupo e parar de receber e-mails dele, envie um e-mail para [email protected]. Para ver esta discussão na web, acesse https://groups.google.com/a/dimap.ufrn.br/d/msgid/logica-l/CAMTR9904PwiET2unpBUCt71oJDYD2VowRi3%2Bu7g8-1u_mDSHvA%40mail.gmail.com.
