Not so fast Walid Saba

We definitely learn common sense

Victor Morgante


One of my newly found and favourite authors on logic, Walid Saba, just posted an article with the title “Why Commonsense Knowledge is not (and can not be) Learned”.

Woh! Now there is a challenge for you. Take it if you dare.

I do.

My research revolves around all of logic falling under game theory and where theorems of a formal system of logic only make sense to any two people if and only if those two people have a shared interpretation and use of that theory of logic. E.g. Ehrenfeucht Fraisse Games can be extended to theories of higher order logic and are not limited to finite model theory.

Let us look at Walid’s claims. He says that when we look at the following sentences we only have one logical common sense interpretation for each:

(1) Jon has a Greek statue in every room in his house
(2) Jon broke his leg when his family had a car accident near Toronto.

The presumed common sense interpretations:

(1) refers not to one, but to many statues since one cannot have a Greek statue (a physical artifact) in more than one location — in NLU lingo, the challenge in (1) is usally in resolving quantifier scope ambiguities. Similarly, a 4-year old knows where Jon broke his leg upon hearing (2), since the location of a sub-event is always the location of the main/larger event. This can be expressed as shown in figure 1 below — the challenge in (2) is in knowing the commonsense logic of events, a logic that will never be explicitly stated in the text.

Not so fast…

  1. It is easy to picture of a house with glass walls and mirrors in every room such that one physical statue results in us believing and thinking that Jon has a multitude of statues.
  2. It is trivially easy to view that Jon broke his leg in New York at the same time that “his family has a car accident near Toronto”.

What I believe differently to Mr Saba is that the ‘common’ and ‘sense’ in ‘common sense’ merely refers to there being an agreement between people when they have a common sense of interpretation of the set of events. That it may be the prevalent sense is neither here nor there, that may be a ‘common’ sense, but others may have, learn and form their own common sense and equally share that in common with others.