In 300BC, a Greek mathematician called Euclid wrote a series of texts called *Elements*. The Elements was a textbook that outlined many principles of mathematics (especially geometry) and it would become one of the most influential works in the history of mathematics. It is composed of a series of axioms (the axiomatic approach) from which many deductions and theorems can be made. Although many of these axioms sound extremely simple and like common sense, the implications are staggering.

The following is **Euclid’s Five Postulates of Plane Geometry**:

- Two points determine a line.
- Any line segment can be extended in a straight line as far as desired, in either direction.
- Given any length and any point, a circle can be drawn having the length as radius and that point as centre.
- All right angles are congruent (can be superimposed).
- Parallel postulate: If two lines intersect a third in such a way that the sum of the inner angles on one side is less than two right angles, then the two lines inevitably must intersect each other on that side, if extended far enough.

Using these postulates, mathematicians are able to deduce more advanced theories. For example, the Elements also describes the famous **Pythagorean theorem**, which states that “in any right triangle, the area of the square of the hypotenuse (the diagonal) is equal to the sum of the areas of the squares of the other two sides” (*a² + b² = c²*).

Thanks to Euclid’s works, we are now able to accurately model and measure the three-dimensional space around us. Not only did Euclid set the foundations for mathematics, his works were also instrumental in the development of logic and modern science.