G-d’s instructions for the building of the altar dictate which materials to use, that the dimensions be equal on every side and that the altar be square (27:1). What is the significance of the requirement for the altar to be square?

Rav S. R. Hirsch explains that creations and buildings with straight lines and angles represent the force of man, who is endowed with the freedom to create and master their surroundings (as opposed to circles which represent organic forces without reasoning). The angles on the altar were so important because they represent the tools and freedoms that we were given to correct wrongs and improve ourselves.