How is Nirvana Samsara in Siddhartha?

Nirvana and
sansara are two common and important terms of Hindu philosophy.
These terms are also equally applicable to Buddhist philosophy which are in essence
variations of the basic Hindu, or if you want to use a non-religion related word,
ancient Indian philosophy. As suggested by Mkcapen in her reply posted above, these
terms may also have been used in the novel Siddhartha, But I am not
aware to what extent the novel correctly reflects the original
concepts.

Sansara is the simpler one
of the two terms. It simply refers to the physical world or the universe that we see and
experience as ordinary human beings. However, as per the Hindu philosophy the world is
not as much of a physical reality as it appears. It exists only as a collection of
perception by the souls occupying the soul, somewhat like a dream seen by a person in
sleep. Just a s person experience joys and distress in a dream, but on waking up the
experiences of the dream appear meaningless, the happiness and miseries of the
sansara experienced by the soul will become when the soul realizes
its true nature. When the soul sort of wakes up. When this happens soul experiences a
sense of extreme ecstasy without any pain or distress associated with the physical life
of sansara.

The soul is unable to come
out of this state of experiencing the sansara because of reasons that we do not need to
go into. But as a result of this inability individual soul must go through repeated
cycles of birth - life - death - and rebirth. Nirvana refers to a
state of realising the true nature of one's soul that leads to release from bondage of
cycle of birth and death.

So we can say that
nirvana is the state of realization of true nature of the soul.
Which also implies the realization of the sansara as being unreal
like a dream.