Interest and Self-Interest

Among the commonest contemporary sources of Profit is one of the oldest, one that pre-dates most Economic institutions--Interest.  But, as is the case with Slavery, at least until recently, age does not justify its continued wide acceptance.  Nor does Interest involve any vital Self-Interest, consisting in merely a combination of Excess and Deficiency, which, as is the case in lending between friends or relatives, can be balanced without recourse to Interest.  To the contrary, a society without Interest might be one absent both living beyond means and a frequent opportunity for exploitation.  Of course, such a society is nowhere in sight at this stage of human history, though the illegalization of slavery might have seemed unimaginable until relatively recently in that history.