### 1.2.4.4 L.E Brouwer

Borrower was a Dutch topologist in the twentieth century. He took up Kronecker's position is that our only building blocks are the natural numbers. All mathematics should be built constructively on the natural numbers. He disagreed with many mathematical devices for proof.

For example there is a mathematical law called the law of trichotomy.
Every number is either zero, positive or negative.
Brouwer gave an example of a real number such that we are unable to prove constructively whether is t is zero positive or negative.
To Brouwer this shows that the law of trichotomy is false.

The number is given on the next page.