As set out in his fine book "Influence: The Psychology of Persuasion". Cialdini lists 6 principles of influence: consistency, reciprocation, social proof, authority, liking, and scarcity.

But - in the first chapter he also lists some tactics and principles that don't seem to come under any of these - e.g. the contrast principle and the use of 'because' that gets higher compliance to a request, even if the reason given is spurious.

So have I missed something and each of these tactics does fall into one of the 6 categories, is the first chapter a ragbag of the things that didn't fit the overall categories but are none the less useful, or what?