 (2) The Ladder Argument (burhān al-sullam): If infinite lines can exist, then there can be an acute angle whose sides are infinite. Suppose that \(AB\) and \(AC\) are two infinite lines which intersect at \(A\) and make such an acute angle. \(AB\) and \(AC\) extend infinitely in the directions of \(B\) and \(C\), respectively. Now consider parallel lines \(B_{i} C_{i}\) (for integers \(i ≥1\)) which intersects \(AB\) and \(AC\) so that the distance between every two consecutive lines is equal to the distance of \(B_{1} C_{1}\) from \(A\). Thus, each line is longer than the previous line by a fixed length, say \(d\) (i.e., for every integer \(i≥1,\) \(B_{i+1} C_{i+1} - B_{i}C_{i} = d\)). Now consider \(BC\). It is farther than any \(B_{i}C_{i}\) from \(A\). Thus, \(BC\) is longer than any \(B_{i}C_{i}.\) This indicates that \(BC\) must be actually infinite. However, \(BC\) is confined between two lines (i.e., \(AB\) and \(AC\)). It terminates at \(B\) and \(C\). Therefore, it must be finite as well. Accordingly, \(BC\) must be both finite and infinite. This is impossible. So, the initial assumption we build the argument upon is false. No infinite line (and, a fortiori, no infinite magnitude) can exist (R. Rashed 2016; 2018: sec. 11.2; Zarepour 2020b: sec. 3.2).