Here is the New Foundations Home Page (NF home page is extremely out of date and needs to be edited, note to self August 2014). Here is the universal set bibliography (an expansion of the bibliography of Forster's NF book). For information about my claim to have proved the consistency of New Foundations, see below.
Here find the slides for my recent talk at the College of Idaho. I'm very pleased with the construction of the reals given there, using neither ordered pairs nor equivalence classes!
Here is my new separate page on the artificial language Loglan.
Here is a purported draft of the proof of the existence of a model of tangled type theory (and thus of Con(NF)).
Here is a fresh take from January 2019, driven by an abstract picture of a scheme for successively adding desired bijections to a specific kind of FM model. Underneath it is the same argument, but I am trying for less mystery.
Here are notes from my summer 2018 visit to Cambridge, involving simplifications of notation, a simplification of the argument, and possibly a reduction in consistency strength to roughly the expected level. These notes are fresh text and so may contain slips and typos, and they are not equipped with the self-contained apparatus of a paper as yet. Here is a further Summer 2018 document in which the FM construction is presented in an abstract way without particular reference to the NF application (and indeed it does have applications to some other related problems).
Here is another rewrite, from January 2018, motivated by a desire to move considerations about clan indices as late as possible in the argument. This is just a zeroth draft of the description of the construction of a tangled web without framing language about how this is used to prove Con(NF), which would be just as in previous versions. The notation in this document is very different from that in the version just below, but the construction and the underlying argument are in fact virtually the same (and could easily be made exactly the same) in a suitable abstract sense: this is strictly a matter of exposition, but improving exposition is a serious issue here.
Here is a completely fresh rewrite of the entire argument, with similar notation and proofs to recent drafts, but an entirely different rhetorical approach: there is no foreshadowing, and on the whole no discussion of intentions. I dive right into the construction and argue forward to the conclusion. This fixes a bug at the very last step of the argument in the just previous draft, it should be noted (which I will fix in the version with repairs). This document is also much shorter than the recent drafts of the submitted paper.
Here is a direct argument for the existence of a model of tangled type theory, similar in approach to the argument just above in some respects, but also similar in essential ways to earlier attempts to build a model of tangled type theory directly. This approach is ghastly in ways which will be evident on reading it, but may have formal advantages.
Here is a possibly useful intuitive overview of the main construction as presented in versions (III(a)) and (IV) below. It's a companion piece to the paper, intended to provide motivations without full arguments whose details become appalling...
As of 3/25/2017, I provide a key to versions. (I) is an ancient version which I preserve because Nathan Bowler's group read it. (II) is the version first submitted to a journal. (IIa) corrects some problems with (II) that I found when preparing (III). (III) is a version with a considerably simplified argument which has been presented to the journal as replacing (II). (IIIa) is a version of (III) with a local correction to one argument. (IV) is a further version with a simplified version of the construction of set parents already suggested in (I).
This (aslnfslides.pdf) is my set of slides for the talk I'll give at the ASL meeting. They are too long, but might be handy as an overview of the proof. (Typos found during the actual delivery of the talk corrected: indeed the notes were too long!)
This (submissiondraft-with-repairs.pdf (IIa)) is a version of the file immediately above which corrects or least remarks on slips in that version which I found in the course of preparing the version now at the top. I commend the version at the top to the reader, but I continue to believe that the argument of this version is basically correct and I'll maintain this for now and update it as required. The argument in the version at the top is simplified, and the bookkeeping is being done differently, but the same system of clans and permutations is intended to be described.
Here is the talk I gave on New Foundations to the department at Boise State on September 10, 2013. Philosophical interests in NF might be served by these slides, and also by the notes on Frege's logic which appear below.
Here (theslides.pdf) are the notes for the talk I gave at the University of Hamburg on June 24, 2015. These have now been extended to a (quite long) full discussion of the proof -- this was done by incorporating a large final segment of the current version of the paper, which needs to be further formatted and cut.
This is my most recent explicitly philosophical essay about Quine-style set theory.
6/4/2016 I have removed various items from here. They still exist: in fact, they are still in the directory pointed to by the links. You may also inquire about them if you are interested.
Here is my latest draft (summer 2017) on representation of functions in third order logic, in a stable version for those currently reading it. Here is my very latest draft (with ongoing revisions)
Here find an outline of a proposed approach to semantics for the Principia Mathematica (PM) of Russell and Whitehead using the type and substitution algorithms in my paper on automated polymorphic type inference in PM. Here find some notes on PM with page references related to the same analysis.
Here find an essay on the ontological commitments of PM and why substitutional quantification does work there and doesn't save you from serious ontological commitments. The flavor of my remarks is admittedly rather bad-tempered; a great deal of nonsense is written about PM.
Here find an outline of how to fix the foundational system of Frege using stratification in the style of Quine. Here find another approach to the same subject. Here find a computer implementation of these ideas.
Here find my current notes on Dana Scott's lovely and weird result that ZFC minus extensionality has the same strength as Zermelo set theory.
Here is the May 19th 2011 (submitted) version of the paper I am writing about Zuhair al-Johar's proposal of "acyclic comprehension", with Zuhair and Nathan Bowler as co-authors, a perhaps surprising reformulation of stratified comprehension.
Here is the Jan 20 2012 draft of the paper I am writing about a simpler form of symmetric comprehension, strong versions of which give extensions of NF with semantic motivation and a weaker version of which gives a new consistent fragment of NF inessentially stronger than NF3, for which I give a model construction. The problem of modelling the versions that yield NF seems to be very hard (as usual). Here is a more recent version with better results on the form of the symmetric comprehension axiom (fewer type levels needed). Here is a still more recent version.
Here find the note submitted Dec 30 2013 on my result that the set H(|X|) of all sets hereditarily smaller in size than a set X exists, not using Choice. It is surprising to me that this is not an obvious result, but the references for partial results that I have been able to find are recent, so perhaps it is new.
Here find a summary of my thoughts on the correct default foundations in the style of Zermelo. In spite of being an NF-iste, I do think that Zermelo-style foundations are the best. However, I think that the axiom of replacement is so strong that it should not be part of the default foundations. In particular, I do not think that the axiom of replacement is justified by the intuition of the cumulative hierarchy; it is a far stronger principle.
Here is a recent version of my manual of logical style, a teaching tool (or would-be teaching tool) with which I am constantly tinkering to try to give students some idea how to approach the precipice of writing a proof.
Here is a draft paper on mathematics in three types (mostly, on defining functions in three types) based on a presentation at BEST 2009. Here are the notes for the talk I gave on this subject in Edmonton on Sept 11 2012. Here is my latest draft (summer 2017) on representation of functions in third order logic.Here is a version of my paper on the curious fact that the urelements in the usual models of NFU turn out to be inhomogeous, because the membership relation on the underlying model-with-automorphism of the usual set theory turns out to be definable in NFU terms. This version corrects a couple of annoying typos in the published version.
I will put a link to my SEP article on Alternative Axiomatic Set Theories here.
Here are my notes on efficient bracket abstraction. Here is a brief related note on eliminating bound variables from syntax.
Here are the notes for the visit of Peter Seymour.
Materials relating to the visit of Olivier Esser are here.
Here's a link to the Department of Mathematics and Computer Science Home Page here at Boise State!
Here is a letter of mine discussing the set theory of Ackermann. Here are some not very serious notes on a pocket set theory. Here is a later version (PDF file).
Here is the official web site of the Loglan Institute. Here is the mirror of the Loglan web site here at Boise State. There is access to a wide variety of information, documents and software through these links.
Here is my new separate page on Loglan, where you can find pointers to my current Loglan projects.