Vertical thinking accounts for about 90% of thinking that is promoted by the present education system.

It is essential in mathematical proofs, in repeating scientific experiments. It uses logic and produces correct answers. The problem is that, as we will see later, not all problems have a correct solution Some complex problems have no solutions others can have many solutions depending on which criteria are adopted.

We first of all provide an example to demonstrate this type of thinking and then we discuss various definitions. The consequences of vertical thinking are presented and some criticisms.