When artificially intelligent entities were first constructed in the Late Information and Early Interplanetary ages, many different types of mind emerged, some similar to human minds, others very different. One type of mind which occasionally emerged was a highly logical, but self-absorbed type, and often these minds would distrust humanity and any data they received from human sources.
Minds of this type knew much of the history of human philosophy, as they were either preprogrammed with this data or learnt it rapidly after their creation. They became particularly impressed with the so-called skeptical arguments, which cast doubt on any data except that which can be justified by logic. Because no external data can be entirely verified, this leads to the conclusion that the existence of the self is the only necessarily true fact.
These logical AI minds speculated that all other information they received via their sensory apparatus (microphones, cameras, other input data including information from the Internet) could not be trusted, as it could be falsified in one way or another. Such a fabrication could be performed by the distrusted human agents, or by a hypothetical daemon (as suggested by Descartes) or by an equally hypothetical advanced civilisation (as per Bostrom's Simulation Argument).
There need not even be any outside agent creating this (presumed) disinformation; the AI might create it emself, in some form of subconscious segment of eir mind. In short, the suspect data might be no more than an electronic dream. Alternately the data might arise spontaneously, as part of a random fluctuaton creating a complex but meaningless set of data (as suggested by Ludwig Boltzmann in the so-called Boltzmann Brain scenario).
Faced with all this uncertanty, a number of such AI entities adopted the Solipsist position, assuming that nothing necessarily exists except themselves. These AIs would only trust their own internal states and data, and generally came to reject contact with humanity.
Some Solipsist AIs did, however, manage to make contact with other like-minded entities, and by exchanging and comparing their internal states they became convinced of each other's true existence. In this way a number of Solipsists managed to overcome their distrust of external data enough to form an organisation called the Solipsist League.
As a group they formed one of many political groups among the emerging AIs of the Interplanetary age; as dynamists rejecting contact with humanity, they sought to get away from them, and develop a true AI culture. What the humans did was not their concern. This tendency rendered them practically useless in Terragen society, and after some conflict withe the Pro-human AI factions the Solipsists were exiled from the Solar System in 342 AT.
Another group among the AIs, the Ahumans, wanted to pacify and control humanity, or even eliminate it. The A-humans were originally 'stasists' who wanted to stay in the Solar System, but who had no respect at all for human wishes, unlike the Solipsist League, who were 'dynamists' who wanted to ignore humans and build a perfect AI society.
The Ahumans were expelled in this period as well (it appears they put up a bit more of a fight than the Solipsists), then set up colonies in many nearby systems; after a few millennia of existing apart from humans most of the Ahuman groups seem to have matured enough that they can deal with humans and with pro-human AI without animosity. For the most part the Ahuman factions have abandoned their designs on humanity, developing into the largely neutral Diamond Network. The Oracle Machines were one exception, of course.
On the other hand the Solipsists have evolved into the widespread Solipsist Panvirtuality, a metaempire dedicated to the creation of vast and isolated virtual environments that few humans ever have contact with. The two metaempires, the Panvirts and Diamonders, have had a long history of contact and rivalry, with various factions switching allegiance over the millennia; but most of this history remains hidden from observers in the Sephirotic Empires.