opencourseware on critical thinking, logic, and creativity

This page is not a tutorial, but a collection of some simple recreational logic puzzles. See if you can solve them!

Stephen was looking at a photo. Someone asked him, "Whose picture are you looking at?" He replied: "I don't have any brother or sister, but this man's father is my father's son." So, whose picture was Stephen looking at?The man in the photo is Stephen's son.

There was a robbery in which a lot of goods were stolen. The robber(s) left in a truck. It is known that : (1) Nobody else could have been involved other than A, B and C. (2) C never commits a crime without A's participation. (3) B does not know how to drive. So, is A innocent or guilty?A is guilty.

Suppose there is this little town with a finite numer of people: (1) No two inhabitants have exactly the same number of hairs. (2) No inhabitant has exactly 409 hairs. (3) There are more inhabitants than there are hairs on the head of any inhabitant. So, what is the largest possible number of inhabitants in that little town?409

In these puzzles you have to work out who is lying and who is telling the truth. There are 382 of them! However, we are sorry that the answers are not provided. So try them with your friends and see if you agree with each other.

Basic logic

- [L01] What is logic?
- [L02] Statements
- [L03] Logical connectives
- [L04] Logical relations
- [L05] Fun logic puzzles
- [L06] The world's hardest logic puzzle!

There are two ways to slide easily through life: to believe everything or to doubt everything. Both ways save us from thinking.

Alfred Korzybski

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