Definition Ladd attributes to ongoing conversations with Scott Bellware. A mistake is not merely a defect or malfunction — in knowledge work, anything that obstructs human understanding qualifies as a mistake, and the target is implementations with no obstructions to understanding. This definition drove Ladd's self-imposed V1 rewrite rules: obey design principles without compromise, correct every discovered mistake immediately along with all its rippling fallout, and start over if he ever lost control of the implementation.