(Canto 1, line 30)
A cryptic line, debated much over the years by scholars. Literally interpreted, it is a description of one's steps in climbing a mountain: to always make sure the lower foot stands firm before taking the next steps. However, based upon Aristotle's theories on physiology, another interpretation reads the "firm foot" as the left one. The left foot was associated with wordly desires by Alberto Magno (1193-1280) and others, and would therefore obstruct the climber on his way to God - it is therefore fitting that it is always lower than the right foot, associated with the intellect. A modern interpretation, by Natalino Sapegno, believes that this line tries to show that Dante still has no solid grip on the virtuous heights he desires to reach, and therefore walks with an unsure gait, always making a conscious effort to stand firmly.