Lecture 3 Natural Language Processing Empirical vs. analytical expressions Restricted quantifiers & literal analysis Partiality; requisites vs. pre-requisites Presuppositions vs. mere entailment Two kinds of negation

Empirical expressions Empirical expressions denote non-trivial (i.e. non-constant) intensions ‘King of France’, ‘the prezident of ČR’, ‘the highest mountain’ denote offices (roles) of type , and actually refer (in this w and t of evaluation) to nothing, Miloš Zeman and Mount Everest, respectively. Yet the referred object must be found out empirically Predicates like ‘to be a student’, ‘to be red’, ‘to be happy’, ‘to be of the age 60’ denote properties of type () and refer to their population, i.e. to a set of individuals who happen to be students, red, happy and of the age 60, respectively. Sentences like “Prague is greater than Brno” denote propositions of type  and refer to a truth-value (this sentence to T). Hence these expressions are empirical, because the object to which they happen to refer in a given state of the world is beyond logical analysis; it can be determined only by empirical investigation of the state of the world at a given time moment.

“No bachelor is married” Analytic expressions Analytic expressions denote extensions or trivial (i.e. constant) intensions The objects they denote and refer to can be determined by mere understanding a given expression, without empirically investigating the state of the world. Mathematical and logical expressions are analytical, they denote extensions Expressions that contain empirical subexpressions are analytical, if they denote constant intensions. Hence the referred object is necessarily, in all worlds w and times t one and the same. “No bachelor is married” “Whales are mammals” Denote the constant proposition True/, that takes value T in all w and t

Restricted quantifiers All students are clever. Some students are lazy. wt x [[0Studentwt x]  [0Cleverwt x]] wt x [[0Studentwt x]  [0Lazywt x]] These analyses are not literal ones, because they are not in harmony with the so- called „Parmenides principle“ and with our method of literal analysis: the sentences do not mention , . Thus we introduce restricted quantifiers All, Some, No, Most, … of type ((())()) [0All M], M v (), v-constructs the set of all supersets of M [0Some M], M v (), v-constructs the set of those sets that have a non-empty intersection with M [0No M], M v (), v-constructs the set of all sets that have an empty intersection with M wt [[0All 0Studentwt] 0Cleverwt] wt [[0Some 0Studentwt] 0Lazywt]

Analytic expressions “No bachelor is married”  True Bachelor, Married/(); No/((())()) wt [[0No 0Bachelorwt] 0Marriedwt] How to prove its analyticity? Let us define and refine: m, n/1 v (), x v : 0No = m n x [[m x]  [n x]], [[0No m] n] = x [[m x]  [n x]]. 0Bachelor = wt x [[0Marriedwt x]  [0Manwt x]]. (to be unmarried and man are requisites of the property of being a bachelor) [[0No 0Bachelorwt] 0Marriedwt] = x [[0Bachelorwt x]  [0Marriedwt x]] = x [[0Marriedwt x]  [0Manwt x]  [0Marriedwt x]]. For every valuation of w, t v-constructs T, thus we can generalize: wt x [[0Marriedwt x]  [0Manwt x]  [0Marriedwt x]].

Necessarily, the number of planets > 5 Quine’s paradox Necessarily, 8 > 5 The number of planets = 8  ??? Necessarily, the number of planets > 5 wt [0> 08 05] (analytical necessity) wt [[0Number_of 0Planetwt] = 08] (empirical fact)  wt [0> [0Number_of 0Planetwt] 05] (empirical fact, not necessary) Types. Number_of/(()): the number of elements of a set; Planet/(); >, =/() Proof: [0> 08 05] 1. assumption, E [[0Number_of 0Planetwt] = 08] 2. assumption, E [0> [0Number_of 0Planetwt] 05] 1, 2 Leibniz, subst. of identicals wt [0> [0Number_of 0Planetwt] 05] 3, I Comment. In the last step we must not introduce , because the variables w, t were bound by  rather than 

Partiality, v-improper constructions Incoherent typing If X is not a construction of order n (n  1), then 1X is improper; (a non-procedural object cannot be executed) If X is not a construction of order n (n  2), then 2X is improper; (a non-procedural object cannot be executed) If X, X1, …, Xn are not constructions typed to produce objects of types according to Def., then [X X1…Xn] is improper by failing to v-construct anything for any valuation v. Example. Tom/; 5/; Student/() 1Tom, 15, wt [0Studentwt 05], 2[wt [0Studentwt 0Tom]] Application of a function f to an argument a such that f is not defined at a [0: x 00] is v-improper for any valuation v x [0: x 00] is not v-improper, as it constructs a degenerate function 0[0: x 00] is not v-improper, as it constructs the Composition [0: x 00] [0Improper 0[0: x 00]] constructs T Improper/(1): the class of constructions v-improper for any v.

Partiality and Compositionality „If five divided by zero equals five, then Tom is the Pope“ denotes the degenerate proposition undefined at all w,t ! wt [[[0: 05 00] = 05]  [0Tom = 0Popewt]]  . 0, 5/; :/(); Tom/; Pope/; [0: 05 00]  ; [[0: 05 00] = 05]  ; 0Tom  ; 0Popewt v ; [0Tom = 0Popewt] v ; [[[0: 05 00] = 05]  [0Tom = 0Popewt]] v . The relation = does not obtain the first argument, hence the implication truth-function also does not obtain the first argument; therefore, the whole Composition is v-improper by failing to construct anything. Partiality is propagated up. The Closure  degenerate proposition

Partiality and Compositionality If you intuitively feel that the sentence could be true, because the speaker wanted to say that it is not true that five divided by zero is five, we must analyse this sentence: „If it is true that five divided by zero equals five, then Tom is the Pope“. True*/(n): the class of those constructions that v- construct T for every valuation v. [0True* 0C] v-constructs T, iff C v-constructs T for any valuation v, otherwise F. wt [[0True* 0[[0: 05 00] = 05]]  [0Tom = 0Papežwt]]   Now the Closure constructs the proposition True. The sentence is analytically true

Partiality and Compositionality False*/(n) and Improper*/(n) are classes of constructions that v-construct F or are v- improper for all valuations v, respectively: [0True* 0C] = [0False* 0C]  [0Improper* 0C] [0False* 0C] = [0True* 0C]  [0Improper* 0C] [0Improper* 0C] = [0True* 0C]  [0False* 0C] Similarly, we often need these properties of propositions: True, False, Undef/()

properties of propositions True, False, Undef/() P,Q   [0Truewt P] v-constructs T if [Pwt = 0T], otherwise F [0Falsewt P] v-constructs T if [Pwt = 0F], otherwise F [0Undefwt P] = [0Truewt P]  [0Falsewt P]

wt [x [[0Truewt wt [0Whalewt x]]  [0Truewt wt [0Mammalwt x]]]] requisities [0Req F G] = wt x [[0Truewt wt [Gwt x]]  [0Truewt wt [Fwt x]]] F, G  () Gloss. The property F is a requisite of the property G iff necessarily, for all x holds: if x happens to be a G then x is an F Examples. “No bachelor is married” “All whales are mammals” [0Req 0Mammal 0Whale] = wt [x [[0Truewt wt [0Whalewt x]]  [0Truewt wt [0Mammalwt x]]]] “The president of CR is a Czech citizen” wt [[0Existwt wt [0Pres-ofwt 0CR]]  [0Truewt wt [0Czech-citisenwt [0Pres-ofwt 0CR]]]] Being a Czech citizen is a requisite of the Czech presidential office

Pre-requisites; presuppositions Tom never smoked Tom stopped smoking Can the second sentence be true or false under the assumption of the first sentence? If Tom never smoked, he couldn’t stop smoking  the sentence (2) is false (?) But then it is true that Tom did not stop smoking  he still smokes (?) The sentence (2), or rather the proposition denoted by (2) has no truth-value Being an ex-smoker is a prerequisite of the property Stop_smoking The presupposition of (2) is the proposition that Tom previously smoked

Pre-requisites; presuppositions Definition (prerequisite relation) Let X, Y be constructions such that X, Y/n  (); x  . Then [0Prereq Y X] = wt [x [[[0Truewt wt [Xwt x]]  [0Falsewt wt [Xwt x]]]  [0Truewt wt [Ywt x]]]]. Gloss definiendum as, “Y is a prerequisite of X”, and definiens as, “Necessarily, any x for which it is true or false that x instantiates X at w, t then x also instantiates Y at w, t.” Corollary. If it is not true that x instantiates the prerequisite Y of the property X then the proposition that x instantiates X is neither true not false, it has not truth-value. Hence, the proposition that x instantiates Y is a presupposition of the proposition that x instantiates X.   The property of being a previous smoker is not only a requisite of the property of having stopped smoking, it is its prerequisite.

Presupposition vs. mere entailment Analytical entailment is defined as follows (P, S/n  , ╞/()). (S╞ P) iff wt [[0Truewt S]  [0Truewt P]] The logical difference between a presupposition and mere entailment is this: P is a presupposition of S iff (S╞ P) and (non-S╞ P) P is merely entailed by S iff (S╞ P) and neither (non-S╞ P) nor (non-S╞ non-P) Comments. If P is a presupposition of S and P is not true at a given w, t-pair, then neither S nor non-S is true. Hence, S has no truth-value at such a w, t- pair at which its presupposition is not true. On the other hand, if P is merely entailed by S, then if S is not true we cannot deduce anything about the truth- value, or lack thereof, of P. Using the properties of propositions True and False, we can rigorously define the difference between presupposition and mere entailment. Definition (presupposition vs. mere entailment) Let P and S be propositional constructions (P, S/n  ). Then P is entailed by S iff wt [[0Truewt S]  [0Truewt P]] P is a presupposition of S iff wt [[[0Truewt S]  [0Falsewt S]]  [0Truewt P]]

Presupposition vs. mere entailment Examples. “The King of Germany is wise” presupposes that “the King of Germany exists” If the King of Germany does not exist, then “the King of Germany is (isn’t) wise” has a truth-value gap, neither true nor false “Police found the murderer of JFK” merely entails that “the murderer of JFK exists” If the unique murderer of JFK does not exist, then it can be true that police did not find the murderer of JFK