Euclidean Geometry as a Base.

Euclid's Elements also include the following five "common notions":
1- Things that are equal to the same thing are also equal to one another.
2- If equals are added to equals, then the wholes are equal.
3- If equals are subtracted from equals, then the remainders are equal.
4- Things that coincide with one another equal one another.
5- The whole is greater than the part.

Conclusion: Equality seems to be the basic geometrical principle which allows for all things to co-exist on the level.