1 # Seminar in Semantics / Philosophy of Language #
3 or: **What Philosophers and Linguists Can Learn From Theoretical Computer Science But Didn't Know To Ask**
5 This course will be co-taught by [Chris Barker](http://homepages.nyu.edu/~cb125/) and [Jim Pryor](http://www.jimpryor.net/). Linguistics calls it "G61.3340-002" and Philosophy calls it "G83.2296-001."
10 * The seminar meets on Mondays from 4-6, in
11 the Linguistics building at 10 Washington Place, in room 104 (back of the first floor).
13 * One student session will be held every Wednesday from 3-4. The other will
14 be arranged to fit the schedule of those who'd like to attend but can't
15 make the Wednesday time. (We first proposed Tuesdays from 11-12, but this
16 time turns out not to be so helpful.) If you're one of the students who
17 wants to meet for Q&A at some other time in the week, let us know.
19 You should see the student sessions as opportunities to clear up lingering
20 issues from material we've discussed, and help get a better footing for what
21 we'll be doing the next week. It would be smart to make a serious start on that
22 week's homework, for instance, before the session.
24 * There is now a [[lambda evaluator]] you can use in your browser (no need to
25 install any software). It can help you check whether your answer to some of the
26 homework questions works correctly.
28 There is also now a [library](/lambda_library) of lambda-calculus
29 arithmetical and list operations, some relatively advanced.
31 * Henceforth, unless we say otherwise, every homework will be "due" by
32 Sunday morning after the Monday seminar in which we refer to it.
33 (Usually we'll post the assignment shortly before the seminar, but don't
34 rely on this.) However, for every assignment there will be a "grace
35 period" of one further week for you to continue working on it if you
36 have trouble and aren't able to complete the assignment to your
37 satisfaction by the due date. You shouldn't hesitate to talk to us---or
38 each other!---about the assignments when you do have trouble. We don't
39 mind so much if you come across answers to the assignment when browsing
40 the web, or the Little Schemer book, or anywhere. So long as you can
41 reason yourself through the solutions and experience for yourself the
44 We reserve the privilege to ruthlessly require you to
45 explain your solutions in conversations at any point, in section or in
48 You should always *aim* to complete the assignments by the "due" date,
49 as this will fit best with the progress of the seminar. Let's take
50 assignment 3 to be "due" on Sunday Oct 3 (the date of this
51 announcement), but as we announced last week in seminar, you can take up
52 until this coming Sunday to complete it. If you need to. Try to complete
53 it, and get assistance completing it if you need it, sooner.
55 * We'll shortly be posting another assignment, assignment 4, which will be
56 "due" on the Sunday before our next seminar. That is, on Sunday Oct 17.
57 (There's no seminar this coming Monday.)
59 The assignments will tend to be quite challenging. Again, you should by
60 all means talk amongst yourselves, and to us, about strategies and
61 questions that come up when working through them.
63 We will not always be able to predict accurately which problems are
64 easy and which are hard. If we misjudge, and choose a problem that is
65 too hard for you to complete to your own satisfaction, it is still
66 very much worthwhile (and very much appreciated) if you would explain
67 what is difficult, what you tried, why what you tried didn't work, and
68 what you think you need in order to solve the problem.
72 To play around with a **typed lambda calculus**, which we'll look at later
73 in the course, have a look at the [Penn Lambda Calculator](http://www.ling.upenn.edu/lambda/).
74 This requires installing Java, but provides a number of tools for evaluating
75 lambda expressions and other linguistic forms. (Mac users will most likely
76 already have Java installed.)
80 ## Lecture Notes and Assignments ##
82 (13 Sept) Lecture notes for [[Week1]]; [[Assignment1]].
84 Topics: Applications; Basics of Lambda Calculus; Comparing Different Languages
86 (20 Sept) Lecture notes for [[Week2]]; [[Assignment2]].
88 Topics: Reduction and Convertibility; Combinators; Evaluation Strategies and Normalization; Decidability; Lists and Numbers
90 (27 Sept) Lecture notes for [[Week3]]; [[Assignment3]].
92 Topics: Recursion with Fixed Point Combinators
94 (4 Oct) Lecture notes for Week 4
96 <!-- Introducing the notion of a "continuation", which technique we'll now already have used a few times
102 ##[[Offsite Reading]]##
104 There's lots of links here already to tutorials and encyclopedia entries about many of the notions we'll be dealing with.
108 ## Course Overview ##
110 The goal of this seminar is to introduce concepts and techniques from
111 theoretical computer science and show how they can provide insight
112 into established philosophical and linguistic problems.
114 This is not a seminar about any particular technology or software.
115 Rather, it's about a variety of conceptual/logical ideas that have been
116 developed in computer science and that linguists and philosophers ought to
117 know, or may already be unknowingly trying to reinvent.
119 Philosphers and linguists tend to reuse the same familiar tools in
120 ever more (sometime spectacularly) creative ways. But when your only
121 hammer is classical logic, every problem looks like modus ponens. In
122 contrast, computer scientists have invested considerable ingenuity in
123 studying tool design, and have made remarkable progress.
125 "Why shouldn't I reinvent some idea X for myself? It's intellectually
126 rewarding!" Yes it is, but it also takes time you might have better
127 spent elsewhere. After all, you can get anywhere you want to go by walking, but you can
128 accomplish more with a combination of walking and strategic subway
131 More importantly, the idiosyncrasies of your particular
132 implementation may obscure what's fundamental to the idea you're
133 working with. Your implementation may be buggy in corner cases you
134 didn't think of; it may be incomplete and not trivial to generalize; its
135 connection to existing literature and neighboring issues may go
136 unnoticed. For all these reasons you're better off understanding the
139 The theoretical tools we'll be introducing aren't very familiar to
140 everyday programmers, but they are prominent in academic computer science,
141 especially in the fields of functional programming and type theory.
143 Of necessity, this course will lay a lot of logical groundwork. But throughout
144 we'll be aiming to mix that groundwork with real cases
145 in our home subjects where these tools play central roles. Our aim for the
146 course is to enable you to make these tools your own; to have enough
147 understanding of them to recognize them in use, use them yourself at least
148 in simple ways, and to be able to read more about them when appropriate.
150 Once we get up and running, the central focii of the course will be
151 **continuations**, **types**, and **monads**. One of the on-going themes will
152 concern evaluation order and issues about how computations (inferences,
153 derivations) unfold in (for instance) time. The key analytic technique is to
154 form a static, order-independent model of a dynamic process. We'll be
155 discussing this in much more detail as the course proceeds.
157 The logical systems we'll be looking at include:
159 * the pure/untyped lambda calculus
160 * combinatorial logic
161 * the simply-typed lambda calculus
162 * polymorphic types with System F
163 * some discussion of dependent types
164 * if time permits, "indeterministic" or "preemptively parallel" computation and linear logic
169 recursion using the Y-combinator
170 evaluation-order stratgies
171 normalizing properties
172 the Curry-Howard isomorphism(s)
173 monads in category theory and computation
176 ## Who Can Participate? ##
178 The course will not presume previous experience with programming. We
179 will, however, discuss concepts embodied in specific programming
180 languages, and we will encourage experimentation with running,
181 modifying, and writing computer programs.
183 The course will not presume lots of mathematical or logical background, either.
184 However, it will demand a certain amount of comfort working with such material; as a result,
185 it will not be especially well-suited to be a first graduate-level course
186 in formal semantics or philosophy of language. If you have concerns about your
187 background, come discuss them with us.
189 This class will count as satisfying the logic requirement for Philosophy
190 PhD students; however if this would be your first or only serious
191 engagement with graduate-level formal work you should consider
192 carefully, and must discuss with us, (1) whether you'll be adequately
193 prepared for this course, and (2) whether you'd be better served by
194 taking a logic course (at a neighboring department, or at NYU next year)
195 with a more canonical syllabus.
198 Faculty and students from outside of NYU Linguistics and Philosophy are welcome
199 to audit, to the extent that this coheres well with the needs of our local
203 ## Recommended Software ##
205 During the course, we'll be encouraging you to try out various things in Scheme
206 and Caml, which are prominent *functional programming languages*. We'll explain
207 what that means during the course.
209 * **Scheme** is one of two major dialects of *Lisp*, which is a large family
210 of programming languages. Scheme
211 is the more clean and minimalistic dialect, and is what's mostly used in
213 Scheme itself has umpteen different "implementations", which share most of
214 their fundamentals, but have slightly different extensions and interact with
215 the operating system differently. One major implementation used to be called
216 PLT Scheme, and has just in the past few weeks changed their name to Racket.
217 This is what we recommend you use. (If you're already using or comfortable with
218 another Scheme implementation, though, there's no compelling reason to switch.)
220 Racket stands to Scheme in something like the relation Firefox stands to HTML.
222 * **Caml** is one of two major dialects of *ML*, which is another large
223 family of programming languages. Caml has only one active implementation,
224 OCaml, developed by the INRIA academic group in France.
226 * Those of you with some programming background may have encountered a third
227 prominent functional programming language, **Haskell**. This is also used a
228 lot in the academic contexts we'll be working through. Its surface syntax
229 differs from Caml, and there are various important things one can do in
230 each of Haskell and Caml that one can't (or can't as easily) do in the
231 other. But these languages also have a lot in common, and if you're
232 familiar with one of them, it's not difficult to move between it and the
235 [[How to get the programming languages running on your computer]]
237 [[Family tree of functional programming languages]]
240 ## Recommended Books ##
242 It's not necessary to purchase these for the class. But they are good ways to get a more thorough and solid understanding of some of the more basic conceptual tools we'll be using.
244 * *An Introduction to Lambda Calculi for Computer Scientists*, by Chris
245 Hankin, currently $17 on
246 [Amazon](http://www.amazon.com/Introduction-Lambda-Calculi-Computer-Scientists/dp/0954300653).
248 * (Another good book covering the same ground as the Hankin book, but
249 more thoroughly, and in a more mathematical style, is *Lambda-Calculus and Combinators:
250 an Introduction*, by J. Roger Hindley and Jonathan P. Seldin. If you choose to read
251 both the Hankin book and this book, you'll notice the authors made some different
252 terminological/notational choices. At first, this makes comprehension slightly slower,
253 but in the long run it's helpful because it makes the arbitrariness of those choices more salient.)
256 * *The Little Schemer, Fourth Edition*, by Daniel P. Friedman and Matthias
257 Felleisen, currently $23 on [Amazon](http://www.amazon.com/exec/obidos/ASIN/0262560992).
258 This is a classic text introducing the gentle art of programming, using the
259 functional programming language Scheme. Many people love this book, but it has
260 an unusual dialog format that is not to everybody's taste. **Of particular
261 interest for this course** is the explanation of the Y combinator, available as
262 a free sample chapter [at the MIT Press web page for the
263 book](http://www.ccs.neu.edu/home/matthias/BTLS/).
265 * *The Seasoned Schemer*, also by Daniel P. Friedman and Matthias Felleisen, currently $28
266 on [Amazon](http://www.amazon.com/Seasoned-Schemer-Daniel-P-Friedman/dp/026256100X)
268 * *The Little MLer*, by Matthias Felleisen and Daniel P. Friedman, currently $27
269 on [Amazon](http://www.amazon.com/Little-MLer-Matthias-Felleisen/dp/026256114X).
270 This covers some of the same introductory ground as The Little Schemer, but
271 this time in ML. It uses another dialect of ML (called SML), instead of OCaml, but there are only
272 superficial syntactic differences between these languages. [Here's a translation
273 manual between them](http://www.mpi-sws.org/~rossberg/sml-vs-ocaml.html).
279 All wikis are supposed to have a [[SandBox]], so this one does too.
281 This wiki is powered by [[ikiwiki]].