The rough equivalent for “soul” in Jainism is “Jiva.” The jiva is subject to constant change by virtue of incarnation but is no longer subject to them when it is free of the body from final liberation from reincarnation. In this respect, Jainism is quite dualistic as a philosophy. The soul pervades the entire body and adjusts its size to fit whatever body it inhabits, pervading the entire organism and keeping it alive as long as it inhabits the body. The Siddha is a liberated jiva not subject to reincarnation and the Sansari jiva is the jiva subject to continual reincarnation.
Oncec karma is exhausted, the jiva is no longer subject to reincarnation and live in a separate part of the universe known as Siddhashila. Here, they possess neither form nor shape but enjoy perfect knowledge, perception and bliss. All exist in a state of total equality. Jivas within spacetime, however, have karma and are continually subject to reincarnation and the suffering that necessarily accompanies it within spacetime. With the exception of Arihants, such jivas are limited in their knowledge and perception. Such jivas navigate spacetime through the five senses. Some cannot move and only have one sense while others move and have between two and five senses. There seems to be a panpsychist element in Jainism, according to which even apparently inanimate objects have some form of jiva. Some plants, furthermore, are understood by Jains as possessing an infinite number of souls.
Celestial beings are understood as the happiest of beings, although they cannot engage in the kinds of ascetic practices that result in salvation. Animals are similarly limited, and it is uniquely the human state that is understood as preferable because it is during this life alone that one can use logic and asceticism by which they can achieve Moksha or salvation through liberation from rebirth. The infernals in hell are seen as the unhappiest of all jivas. This model of the relationship between happiness and incarnation is similar to what we find in certain schools of Buddhism.