While a significant minority of the galactic population is considered strongly religious (see NEWS RELIGION), the Twis'rin state religion is noteworthy both for its belief system and for the fervour with which the Twis'rin believe in it. Not for they, the seperation of church and state: since long before first contact the Twis'rin have had only one religion to speak of and it has merged with their society to such an extent that a Twis'rin considering, for example, a school not based in religious teachings is as foreign as considering water that is not wet.

Though their religion, when expressed in English, can only be couched in metaphor, their beliefs are still relatively simple. They believe that the universe is in essence one large ocean, with the planets and the stars merely caves or rocks in this ocean. Each ocean is surrounded by a larger one and contains a smaller one: in the 'higher levels' dwell more primitive beings, and the lower one gets the more advanced the species in question. Though there is no god as such, the Twis'rin hold subatomic particles as the very highest forms of matter; for a long time, the method by which nuclear weapons functioned were kept secret from the people to prevent an outcry at atoms being smashed together so uncouthly.

Most importantly, the Twis'rin consider themselves, by virtue of living in the literal oceans, as the very pinnacle of sentient life. "Land-dwellers" live in the next ocean out and are therefore inevitably inferior to the Twis'rin. If a Twis'rin lives his life well, he will return as a molecule or an atom somewhere in the universe. If he lives badly, he will stuck being a cat or a Balorim or something similarly uncouth. Thus, so long as they have been able to, the Twis'rin have treated land-dwelling species like most treat mosquitos. Only the amphibious Captab, who are most comfortable in the water, confound the Twis'rin spiritual system: theoretically, the Captab should be equals to the Twis'rin, but thousands of years of bred-in xenophobia do not dispel easily, and most Twis'rin view the Captab not as spiritual cousins but as pretenders; the lowest of the low.

The Twis'rin religion idolises various prophets and martyrs, but they do not have a god as such. The Twis'rin religion also lacks prayer and most observances are made in the form of quiet meditatioon on the nature of the universe. However, in times of stress a Twis'rin will often be caught mumbling to the "spirits of the galaxy" who supposedly dwell within the leptons and quarks to get him through a tight patch.