As the article mentions log( n! ) is the theoretical lower bound on the comparison sorting unstructured data. This is a neat little argument so I thought I'd share it with you. Given an unsorted list of data (of length n), sorting is equivalent the discovering the permutation that will return the elements to their correct order. Now there are a total of n! possible permutations that we need to sift through. Now each comparison can be thought of as a yes-no, since we've all played 20 questions, I assume we all have noticed that with m yes-no questions we can distinguish between 2^m possibilities. Thus we need 2^m = n! ie m = log2(n!). Giving us our bound.