Lecture 1: Quick Intro to FOL

Question 1

Sentence .E.G. (John is Square)

Answer 1

For now a sentence is just something capable of being true or false.

Question 2

name

Answer 2

Refers to an object

Question 3

Predicate

Answer 3

Predicates are things that refer to properties.

Question 4

or

Answer 4

connective (joins sentences)

Question 5

non-atomic sentences

Answer 5

a sentence with one or more connectives is ‘non-atomic’

Question 6

atomic sentences

Answer 6

atomic sentences (no connectives)

Question 7

Write John is Square in FOL

Answer 7

Square(a)
the letter a is a name; just like the English name John, the function of ‘a’ is to refer to an object (in this case John).
Square( ) is the predicate

Question 8

John is to the left of Ayesha in FOL?

Answer 8

LeftOf( a,b)
the single letters a and b are names.
And ‘LeftOf( )’ is the predicate. Note that, as in English, the order of the names matters. It affects who we are saying is to the left of who.

Question 9

John is square or Ayesha is triangular in FOL?

Answer 9

Square( a ) ∨ Triangular( b )

This is a non-atomic sentence

Question 10

Why do we need a formal language such as FOL?

Answer 10

We need a formal language because ambiguity is awkward to deal with theoretically
Appearance and reality. We need a formal language because we want a guarantee that a sentence which seems to express a proposition really does express a proposition.