What is the general theme of Rumi's thought?

"The general theme of Rumi's thought, like that of other mystic and Sufi poets of Persian literature, is essentially that of the concept of tawhīd – union with his beloved (the primal root) from which/whom he has been cut off and become aloof – and his longing and desire to restore it"

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The lover's cause is separate from all other causes

Love is the astrolabe of God's mysteries.[36]

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Rumi was an evolutionary thinker in the sense that he believed that the spirit after devolution from the divine Ego undergoes an evolutionary process by which it comes nearer and nearer to the same divine Ego.^[48] All matter in the universe obeys this law and this movement is due to an inbuilt urge (which Rumi calls "love") to evolve and seek enjoinment with the divinity from which it has emerged. Evolution into a human being from an animal is only one stage in this process. The doctrine of the Fall of Adam is reinterpreted as the devolution of the Ego from the universal ground of divinity and is a universal, cosmic phenomenon.^[49] The French philosopher Henri Bergson's idea of life being creative and evolutionary is similar, though unlike Bergson, Rumi believes that there is a specific goal to the process: the attainment of God. For Rumi, God is the ground as well as the goal of all existence.

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The nation of Love has a different religion of all religions - For lovers, God alone is their nation and religion
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Universality

It is often said that the teachings of Rumi are ecumenical in nature.^[51] For Rumi, religion was mostly a personal experience and not limited to logical arguments or perceptions of the senses.^[52] Creative love, or the urge to rejoin the spirit to divinity, was the goal towards which every thing moves.^[52] The dignity of life, in particular human life (which is conscious of its divine origin and goal), was important.^[52]

ملت عشق از همه دین هاجداست - عاشقان را مذهب و ملت خداست

The nation of Love has a different religion of all religions - For lovers, God alone is their nation and religion

Islam

However, despite the aforementioned ecumenical attitude, and contrary to his contemporary portrayal in the West as a proponent of non-denominational spirituality, a number of Rumi poems suggest the importance of outward religious observance, the primacy of the Qur'an.^[53]

Flee to God's Qur'an, take refuge in it
there with the spirits of the prophets merge.
The Book conveys the prophets' circumstances

those fish of the pure sea of Majesty.^[54]

Seyyed Hossein Nasr states:

One of the greatest living authorities on Rûmî in Persia today, Hâdî Hâ'irî, has shown in an unpublished work that some 6,000 verses of the Dîwân and the Mathnawî are practically direct translations of Qur'ânic verses into Persian poetry.^[55]

Rumi states in his Dīwān:

The Sufi is hanging on to Muhammad, like Abu Bakr.^[56]

His Masnavi contains anecdotes and stories derived largely from the Quran and the hadith, as well as everyday tales.

On the first page of the Masnavi, Rumi states:

"Hadha kitâbu 'l- mathnawîy wa huwa uSûlu uSûli uSûli 'd-dîn wa kashshâfu 'l-qur'ân."
This is the book of the Masnavi, and it is the roots of the roots of the roots of the (Islamic) Religion and it is the Explainer of the Qur'ân.

The famous (15th century) Sufi poet Jâmî, said of the Masnavi,

"Hast qur'ân dar zabân-é pahlawî"
It is the Qur'ân in Persian.

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Recordings of Rumi poems have made it to the USA's Billboard's Top 20 list. A selection of American author Deepak Chopra's editing of the translations by Fereydoun Kia of Rumi's love poems has been performed by Hollywood personalities such as Madonna, Goldie Hawn, Philip Glass and Demi Moore.
http://en.wikipedia.org/wiki/Rumi