Things which coincide with one another are equal to one another. The whole is greater than the part. It is possible to draw a straight line from any point to any point. It is possible to produce a finite straight line continuously in a straight line. It is possible to describe a circle with any centre and distance.
All right angles are equal to one another.
If a straight line falling on two straight lines make the interior angles on the same side less than two right angles, the two straight lines, if produced indefinitely, meet on that side on which are the angles less than the two right angles. Together, these common notions and postulates represent the axioms of Euclid's geometry. An axiom is a logical principle which is assumed to be true rather than proven, and which can be used as a premise in a deductive argument. Euclid goes on in his Elements to present various geometric propositions, and shows them to be true using deductive inference within his axiomatic system. Euclid's proposition 6.