The body of mentally-integrated knowledge/facts/factoids/beliefs/preconceptions which a person or a community holds to be true.
In practical memetics, a thorough knowledge of this system and its relationships is used to ensure that newly introduced memes are likely to be accepted as facts. For example, in marketing or politics a memeticist who is aware of particular likes or dislikes and accepted truths in the subject person or population will almost certainly apply similarity factors between their own products/goals and the subject's likes as well as between competitors' products/goals and the subject's dislikes; the ideal result is that the memeticist's goals/product are accepted as desirable by the target without any explicit decision-making process. Manipulations of precursor knowledge been common within groups of sophonts since before the dawn of civilization, but beginning in the Information Age this practice became a science rather than an art.
Manipulations involving precursor knowledge can be quite powerful within a toposophic level, especially when they are carried out by large organizations, but when beings of a higher toposophic level take an interest in manipulating precursor knowledge of ordinary sophonts the effect may be overwhelming. This was true even in among the relatively primitive and scattered S1 transapients known to Terragen history. From the fragmentary records that survived the Technocalypse, it is apparent that leading AI researchers and institutes were in the memetic thrall of their creations. Apparently the degree, kind, and intent of influence varied, but this helps account for the fact that the first transapients went undetected for so long and were considered to be, at most, superbright/superturing entities. Similarly the first known S2 transapient, GAIA, was not recognized as a new sort of being by the S1 community of the day until well after her transcension and even though she was alone and relatively new, a primitive by the standards of modern S2 transapients, she was able to shape the entire Terragen civilization of the day to her purposes. Such manipulations continue into the present day, varying from the apparently minimal and benign influence of transapients in the Sephirotics and in the 'Civilized Galaxy' generally to the much more variable effects of the various 'Ahuman' and 'Anti-human' powers.