Citations in your CV

I drank the Koolaid and set up my CV so it’s generated automatically from a YAML file with a Pandoc template. The basic functionality is copied from bmschmidt/CV-pandoc-healy. My version generates the bibliography from a BibTeX file however, using biblatex.  The biblatex code is tweaked to include links to PhilPapers and Google Scholar citation counts.

The whole thing is on Github.

A Fistful of Commits

I just checked in a whole bunch of changes to the part on first-order logic. Most of it is in preparation for a new version of the Logic II textbook Sets, Logic, Computation, which Nicole is planning to use in the Fall term.  Also important, and that’s why I put it right here at the top:

PDFs now live on builds.openlogicproject.org. The builds site has a nice index page now rather than a plain file list. If you link to a PDF on my ucalgary site, please update your link; that site will no longer be updated and will probably disappear sometime soon.

Here’s a list of changes:
  • I’ve revised the completeness theorem thoroughly. (This was issue 38.) The main change is that instead of constructing a maximally consistent set, we construct a complete and consistent set. Of course, those are extensionally the same; but both the reason for why we need them and the way we construct them is directly related to completeness and only indirectly to maximal consistency: We want a set that contains exactly one of A or ¬A for every sentence so we can define a term model and prove the truth lemma. And we construct that set by systematically adding either A or ¬A (whichever one is consistent) to the original set. So it makes pedagogical sense to say that’s what we’re doing rather than confuse students with the notion of maximal consistency, prove that the Lindenbaum construction yields a maximally consistent set, and show that maximally consistent sets are complete so we can define the term model from it. Credit for the idea goes to Greg Restall, who does this in his course on Advanced Logic.  (I kind of wonder why standard textbooks mention maximally consistent sets. I’m guessing it’s because if you consider uncountable languages you have to use Zorn’s lemma to prove Lindenbaum’s theorem, and then using maximality is more natural. Is that right?) A bonus effect of this change is that a direct proof of the compactness theorem is now a tedious but relatively easy adaptation of the completeness proof; and I’ve added a section on this (leaving most of the details as exercises).
  • I’ve revised the soundness proofs for sequent calculus and natural deduction, where the individual cases are now more clearly discussed. (This was issue 74 and issue 125.)
  • In the process I also simplified a bunch of things, filled in some details, and corrected some errors. This includes fixing issue 110, and cleaning up the whole stuff about extensionality. There is a new section on assignments which you may need to add to your driver file unless you include fol/syn/syntax-and-semantics.tex in its entirety.
  • The natural deduction system now uses Prawitz’s standard rules, i.e., the double negation elimination rule has been replaced with the classical absurdity rule, and the negation rules are now the special cases of the conditional rules with ⊥ as consequent. This was issue 144. Comparing the system to other treatments in the literature is now easier, and the chapter will integrate more seamlessly with the part on intuitionistic logic that’s in the works.
  • The sequent calculus chapter now uses sequents that are made up of sequences, not sets, of formulas. This was issue 145. This is the standard way of doing it, and will make it easier to add material on substructural logics. It also makes the soundness proof a lot easier to understand.
  • In both the sequent calculus and natural deduction chapters, the material on quantifiers is now separated from that on propositional connectives. Eventually it should be possible to present propositional logic separately (or only), and now you can reuse only the material on propositional logic. (This was issue 77.)
  • There is a new chapter on proof systems, and the intro sections from both the natural deduction and sequent calculus chapters have moved there. So if you only want one of the proof systems, you’ll have to include the relevant intro section in the chapter on the proof system “by hand.” But if you include both, you now have an additional chapter that introduces and compares them.  (This was issue 61.)
  • Sets, Logic, Computation (the textbook for Logic II) now includes both sequent calculus and natural deduction!
Note: The formatting of the rules in both systems now uses a defish (“definition-ish”) environment. If your remix uses a custom -envs.sty file, you will need to add a definition for that at the end (see open-logic-envs.sty). The textbooks for Logic II and Logic III have been updated accordingly.

Illuminated Manuscript of Aristotle, Averroes, and Ramon Llull Charging the Tower of Falsehood

Jonathan Greig (LMU Munich) posted the picture above to Twitter the other day, crediting Laura Castelli with finding it. It’s from a 14th Century illuminated manuscript by Thomas Le Myésier, Breviculum ex artibus Raimundi Lulli electum, and depicts Aristotle, Averroes, and Ramon Llull leading an army charging the Tower of Falsehood. I put a full resolution version here. It’s really amazing.

Here’s the (Google translated, too lazy to thoroughly revise, maybe I’ll get back to it if anyone needs me to) description from the university library at the University of Freiburg  (complete German original):

Miniature VI shows the army of Aristotle, which is advancing to destroy the tower of untruth, together with the commentator of Aristotle, Averroes (Exercitus Aristotillis ad destruendum turrim falsitatis cum suo commentatore). The tower of untruth is occupied by the messengers of untruth: left wickedness, inactivity, ignorance, weakness, confusion, fall, futility, nothingness; Right smallness, impossibility, hatred, untruth, punishment, contrast, emptiness, inflexibility, abundance, diminution (malitia, cessatio, ignorantia, debilitas, confusio, casus, frustra, nihil and parvitas, impossibilitas, odiositas, falsitas, poena, contrarietas, vacuum, difformitas, superfluum, diminutum). To the left of the tower, at the vanguard, the goal is stated: to take down the tower by destruction or distinction (Per interemptionem aut per distinctionem oportet dissolvere turrim). The shield affirms credible reasoning, the text above above the archer, excellent proof (Probabiliter arguo, Potissime demonstro).  The horse of Aristotle is rational reasoning (ratiocinatio), his lance represents “instruments abundunt in syllogisms”, the banner mentions the methods: consideration of the similar, exploring differences, use of proposition, distinction of diversity (consideratio similitudinum, inventio differentiarum , Sumptio propositionum, multiplicis distinctio). In the chariot, the five predicates or general statements of logic are found in the front: general genus, special kind, universal difference, peculiarity, accidental property (genus generalissimum, species specialissima, differentia generalis, proprietas, accidens). Behind this are the ten categories of ontology, ten simple principles of things (Decem rerum principia incomplexa). The text beside the lance of substance specifies “by itself, originally, first, by virtue of itself: per se, principaliter, primo, propter se subsistens.” The rest of the categories are characterized summarily on the banner by the fact that they are not in themselves, but are the substance in itself (Non sumus propter nos, sed ut sit substantia, see Ideo, quia ab ea dependemus, sibimet inhaeremus).

The following banner is carried by Averros riding on his horse, which represents the imagination (imaginatio). The principles of his philosophy of nature are listed on the banner: purpose, effect, form, material, deficiency (finis, efficiens, forma, materia, privatio). The three texts next to his lance read: To be perfect in speculation and to train in them is the highest happiness (Esse perfectum in speculativis and in ice exerceri summa est felicitas); The faith of the heretic Averroes is in every law (Fides Averrois haeretici in omni lege); The next to the lance of the first warrior it reads: body in its quantity, movement, time, external appearance, place, natural observation (Corpus quantum, motus, tempus, superficies , Locus, consideratio naturalis), next to that of the second, the Aristotelian saying (according to Metaphysics, 993b): just as the eye of the night owl is to sunlight, our intellect is related to what is evident in its nature. The Pope with a cross in his hands and the abbreviated “Te Deum” text, a bishop with a prayer (Deus misereatur nostri et benedicat nobis) and below a cardinal, restraining Averroes, with the texts: “Because the phenomena can not exceed the physical nature, your intellect is obscured for what is recognizable in the purely spiritual, Averroes! So that you do not lead us into temptation, we will curb your course, for it is a sacred duty that, when one must be elected among several friends, the truth is preferable.” The banner reads,”Socrates is a friend, but truth is more a friend” (Socrates amicus, sed magis amica veritas). In the lecture of the cardinal, which follows below, this is further elaborated by referring to the limits of Averroistic philosophy and the spiritual power of the Church with the pope, episcopate, clergy, religious and theologians. He concludes with the sentence: “Nevertheless, in physical and metaphysical truths, they allow you to advance on the tower of untruth, to destroy it together with others who wish to free truth from the dungeon of untruth with the help of God.”

The text at the bottom left of the page is a lamentation of the truth: “In the dungeon of this tower, truth was incarcerated against its nature, and it languishes to be free from all the world and cry, crying and crying horribly:” Have mercy, have mercy With me, at least you, my friends! The hand of ignorance touched me, and in my place the unreliable opinion was crowned in public; I, on the other hand, which I fear from every angle, is entirely hidden from my will in the darkness and without light in the depths of the dungeon. Sad, deserted and almost desperate I die! There is no one to help me or give me comfort. On the contrary, many are more inclined to support the wrong opinion than to free me from the dungeon. All your philosophers, apart from God, I place all my trust in you, because you are true lovers of wisdom and truth, come to my aid, I beg you; Otherwise I must perish by inaction. Oh, Christian lords, how can you bear to be so oppressed by Jews and Saracens that I should fall from the top of the tower, which I should even pass, into the dungeon of this tower of untruth? ”

The miniature VII shows the approaching substitute army of Raimundus for the destruction of the tower of untruth and ignorance (Retrobellum et succursus exercitus domini Raimundi Lul de Maioricis ad corruendum turrim falsitatis et ignorantiae). The three trumpeters symbolize the three forces of the rational soul: recognizing, loving, honoring, referring to God, to the triads, to the Creator and the Savior, each in a permutating order (Deum cognoscamus, diligamus, recolamus, Unum Deum trinum diligamus, recolamus, Cognoscamus, Creatorum nostrum recolamus, cognoscamus, diligamus, nostrum redemptorem). Beside the trumpets are the three soul-forces: reason, memory of the will (intellectus, voluntas, memoria). The addition of another hand in the lower left shows that only one horse is represented here (Deberet esse unus equus tantum). An example of how Thomas Le Myésier inspected the finished images and corrected them in this case.

Lull’s horse bears the name of the right or good intent (recta intentio). The motto next to his lance reads: “He who wants to recognize the spiritual must pass over the senses and the imagination, and often himself” (Intelligent spiritualia oportet sensus et imaginationem transcendere et multotiens seipsum). On the banner, “we love God through the first intention and the greater goal” (Per primam intentionem et miioritatem finis Deum diligimus, Per secundam intentionem et minoritatem finis meritum spectamus). The eighteen principles of the Lullian Ars are recorded in the car: the nine absolute principles: goodness, greatness, duration, power, wisdom, will, virtue, truth, glory, bonitas, magnitudo, duratio, potestas, sapientia, voluntas, virtus, veritas, gloria).

To the absolute follow the nine relative principles: difference, agreement, opposition, beginning, middle, goal, greaterness, equality, minority (differentia, concordantia, contrarietas, principium, medium, finis, maioritas, aequalitas, minoritas); In the latter three the inscriptions and lances are missing. The fire column between the two groups, in reference to Exodus 13: 20-22, could symbolize the presence of God in the battle. The commentary text under the figure is: “Raimundus rides on the horse” good intention “(recta intentio) and follows the cross and the holy Catholic faith.) He sends three trumpeters ahead: the three forces of the reasoning elegans And the Son of God, Jesus Christ, who was crucified, who sought to recognize, love, glorify, and glorify God through His Ars For it is much appreciated by him, lovable, venerable, and worthy of gratitude, which must be our basic intention, a true intention, in contrast to that of Averroes, who did not know the truth, Not because he has disapproved of it as much as he can, but denies eternal life, asserts that the happiness is in the observation that it is perfect in the speculative sciences. He does not turn to the inner activity of God; As well as not of his creative outward activity, not taking care of the fact that every activity is directed towards the goal and the perfection. Neither did he care to recognize the nature of divine dignities or their activities, neither their unity, nor their personal distinction of activity, without which God would forever remain inactive in himself, and without any dignity. Consequently, in his whole nature he would be imperfect and ultimately unworthy to be God. But he himself has revealed himself as the most perfect, simple, uniquely, and purest act recognizing himself; But without one who knows, one can recognize one who is recognizable and the act of cognition, namely, the cognition itself, which can not be recognized by the one who recognizes eternally. Through this activity, we recognize necessarily the personal trinity as a unity in essence. Through their external activity, we recognize the creation of the world and the order of their parts, which God did not create infinite wisdom for no purpose and without goal, but arranged for the greater attainment of the goal. For God and nature do nothing in vain, as even the ancient philosophers and their first confess.”

New in Print: forall x (Summer 2017 edition), and Incompleteness and Computability

New on Amazon: the print version of the Summer 2017 edition of forall x: Calgary Remix, as well as the text I made for Phil 479 (Logic III) last term, Incompleteness and Computability. The new edition of forall x includes a number of corrections submitted by Richard Lawrence, who taught from it at Berkeley in the Spring term. I’ve also noticed that if you don’t want Amazon to distribute the book to libraries and bookstores, you can make it a lot cheaper: USD 7.62 instead of USD 11.35.  Of course, the PDF is still free. (There’s now also a version for printing on letter-sized paper.) With Richard’s and Aaron’s help, the solutions manual now matches the text and has fewer errors.

Links to Amazon: US UK Canada Germany

The print version of Incompleteness and Computability incorporates a number of corrections and improvements suggested by my Logic III students. Compared to the version announced earlier, it also includes the two new chapters on Models of Arithmetic and on Second-order Logic. It, too, is still available free in both PDF and source code.

Links to Amazon: US UK Canada Germany

Aldo Antonelli’s last paper

Aldo Antonelli’s last paper, “Completeness and Decidability of General First-Order Logic (with a Detour Through the Guarded Fragment)” is now out in the most recent issue of the Journal of Philosophical Logic.

This paper investigates the “general” semantics for first-order logic introduced to Antonelli (Review of Symbolic Logic 6(4), 637–58, 2013): a sound and complete axiom system is given, and the satisfiability problem for the general semantics is reduced to the satisfiability of formulas in the Guarded Fragment of Andréka et al. (Journal of Philosophical Logic 27(3):217–274, 1998), thereby showing the former decidable. A truth-tree method is presented in the Appendix.

It is published together with a note on it by Hajnal Andréka, Johan van Benthem, and István Németi in the same issue.

Association for Symbolic Logic at the Pacific APA

The ASL Spring Meeting will take place on Wednesday and Thursday at the Pacific APA in Seattle! Note that the ASL Reception will take place on Thursday, April 13, 5:00–7:00 p.m. There will be snacks and wine!

Here’s the program:

WEDNESDAY MORNING, APRIL 12, 9:00 A.M.–12:00 P.M.

Invited Speaker Session: MODALITY AND MODAL LOGIC
Chair: Audrey Yap

Peter Fritz (Universitetet i Oslo), A philosophical perspective on algebraic models for modal logics.

Fenrong Liu (Tsinghua University), Social epistemic logic.

Tamar Lando (Columbia University), Topology and measure in logics for point-free spaces.

WEDNESDAY AFTERNOON, APRIL 12, 1:00–4:00 P.M.

Invited Speaker Session: INTUITONISTIC MATHEMATICS AND LOGIC
Chair: Valeria de Paiva

Mark van Atten (Centre National de la Recherche Scientifique and Université Paris 4), Intuitionism and impredicativity.

Rosalie Iemhoff (Universiteit Utrecht), Quantifiers and functions in intuitionistic logic.

Joan Rand Moschovakis (Occidental College), Realizable extensions of Brouwer’s analysis.

THURSDAY MORNING, APRIL 13, 9:00 A.M.–12:00 P.M.

CONTRIBUTED TALKS
Chair: Richard Zach

Joachim Mueller-Theys, Defining and simplifying the second incompleteness theorem.

Valeria de Paiva and Harley Eades III, Dialectica categories for the Lambek calculus.

Ronald Fuller, First-order logic in 13th-century accounting systems.

Rachel Boddy (University of California, Davis), Fruitful definitions.

Michael McGrady, Garbage collection (GC), Gödel numbering, and periodicity in mathematical logic.

Fabio Lampert (University of California, Davis), On the expressive power of propositional two-dimensional modal logic.

Alexei Angelides (University of San Francisco), Weak arithmetics and the bar rule.

THURSDAY AFTERNOON, APRIL 13, 1:00 P.M.–4:00 P.M.

Special Session organized by the Committee on Logic Education: INCLUSIVENESS IN LOGIC EDUCATION
Chair: Alexei Angelides

Audrey Yap (University of Victoria), Symbolic logic, accessibility, and accommodation.

Fenrong Liu (Tsinghua University), Experiences and difficulties in teaching logic at Tsinghua University.

Nicole Wyatt (University of Calgary), The Open Logic Textbook.

Maureen Eckert (University of Massachussetts, Dartmouth), The Summer Program for Diversity in Logic: Some reflections.

Panel discusssion.

THURSDAY EARLY EVENING, APRIL 13, 5:00 P.M.–7:00 P.M.
ASL Reception

New Textbook on Incompleteness

I made a textbook on incompleteness for my Logic III course. See it/read about it over at the Open Logic Project.