The argument of the new book, Tradition and Influence

A meme is a replicated bit of human culture. Memes evolve through Darwinian processes of differential survival and replication mediated through the human perceptual and cognitive systems. Memes combine into meme-plexes, which are then subject to selection as groups. One meme-plex has influenced another when a significant portion of the second meme-plex contains sub-units that have come from the first. A tradition is a special case of influence in which some elements of the structure of the meme-plex have caused it to be preserved substantially in the same form across multiple generations (i.e., the subsequent meme-plex contains all or nearly all the sub-units of the antecedent meme-plex and no others). The structure of traditional meme-plexes includes three components, recognitio, actio and justificatio, with the justificatio component either in the process of becoming or having become the Universal Tradition Meme: ‘because we have always done so.’ Each of the three aspects of a tradition is subject to different selection pressures. The presence of the Universal Tradition Meme produces selection pressure for traditions to link up with each other. The stability caused by traditions enables certain cultural phenomena, including traditional referentiality and communicative economy. Text-based traditions operate somewhat differently from traditions that are not textual, but the underlying processes are the same. The details of these processes and their interaction with the ever-changing physical and cultural world is the subject of the rest of this book.

Good question by John Cowan below: How is this different from my How Tradition Works. What I've presented above is the core argument of the theory, and it has evolved somewhat substantially since How Tradition Works, since I have refined and extend it in a variety of areas and tweaked the argument throughout. The most significant changes are my recognition that I could not just keep waving my hands at the problems of the perceptual, congitive and mnemonic systems, that instead had to go and try to learn a bunch of material about cognitive psychology, and that the variation and mediation imposed by these systems is responsible for both change and stability in memetic population.
Also, the big thing about this book is that we can see influence in action, even though that action behind the scenes in a way. We've developed "lexomic" techniques to detect influence, and we can even explain, statistically and mathematically, how we can do this. So the ideas (somewhat changed) of the old How Tradition Works are in Tradition and Influence, but the new book is a much-more-developed approach.