This thread is dedicated towards understanding the philosophy behind Arya Samaj and its founder Maharishi Swami Dayanand Saraswati 
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/hinduism/2514-arya-samaj-maharishi-swami-dayanand-saraswati.html
Swami Dayanand (1824-1883), born on 12th February 1824 (in Tankara in the state of Gujurat, India), was the founder of the Hindu reform organization Arya Samaj , which he established on April 7th 1875, in Bombay India. He also created the 10 principles of Arya Samaj. Throughout his life, Swami Dayanand preached against many Hindu traditions which he felt were dogmatic and oppressive. These included traditions such as idol worship, caste by birth, and the exclusion of females from the study of the Vedas. One of his main messages was for Hindus to go back to the roots of their religion, which are the Vedas. By doing this, he felt that Hindus would be able to improve the depressive religious, social, political, and economic conditions prevailing in India in his times.
One of Swami Dayanand's major arguments for going back to the Vedas was that, in his own words " the four Vedas, the repositories of knowledge & religious truth, are the Word of God. They are absolutely free of error, & the Supreme & independent authority ". The four Vedas are; Rig Veda, Yajur Veda, Sama Veda, & Atharva Veda. To spread awareness of his movement and to revitalize Vedic knowledge, Swami Dayanand published many religious books. These include; Satyartha Prakash ( The light of Truth ), the Rig-Vedaadi, Bhasyya- Bhoomika, and Sanskar Vidhi.
Swami Dayanand preached many messages to Hindus during his lifetime. For instance, he preached that Hindus should worship just one, formless, God. He fought against polytheism by telling people the true meaning of the names of God, & established how all of them pointed at one & the same God- Paramathama, the Supreme Self. Further, Swami was " a voice against superstition, against unrighteousness, which reigned supreme in the garb of true religion, and against a foreign rule".
Throughout his known adult life, Swami's main message was " Back to the Vedas ". By this, Swami Dayanand meant that Hindus should stop practising beliefs such as idol worship, caste, polytheism, pantheism, untouchability, child marriages,forced widowhood, and many other practices which he felt were wrong. He challenged many of the Hindu orthodoxy if they could justify their belief in the aforementioned practices. This induced the anger and wrath of many orthodox Hindus, which subsequently led to 14 attempts at poisoning Dayanand. Miraculously, he was able to use his Yogic abilities to cure himself from the first 13 attempts. However, the 14th time proved fatal. Swami Dayanand died, and left the world with his legacy, Arya Samaj.
Arya Samaj - The 10 Principles Principle One: God is the original source of all that is true knowledge and all that is known by physical sciences.
Principle Two: God is existent, Conscious, All Beautitude, Formless, Almighty, Just, Merciful, Unbegotten, Infinite, Unchangeable, Beginningless, Incomparable, the support of All, the Lord or all, All-pervading, Omniscient and Controller of All from within, Evermature, Imperishable, Fearless, Eternal, Pure and Creator of the universe. IT alone must be worhipped.
Principle Three: The Vedas are the books of all TRUE knowledge. It is the paramount duty of all Aryas to read them, to teach them to others, to listen to them and to recite them to others.
Principle Four: All persons should always be ready to accept the truth and renounce the untruth.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=2514 Principle Five: All acts ought to be performed in conformity with dharma (Righteousness and Duty) i.e. after due consideration of the truth and the untruth.
Principle Six: The primary object of the Arya Samaj is to do good to the whole world i.e. to promote physical, spiritual and social progress of all humans.
Principle Seven: Your dealings with all should be regulated by love and due justice in accordance with the dictates of dharma (righteousness).
Principle Eight: Avidyaa (illusion and ignorance) is to be dispelled, and Vidyaa (realisation and acquisition of knowledge) should be promoted.
Principle Nine: None should remain satisfied with one's own elevation only, but should incessantly strive for the social upliftment of all, realise one's own elevation in the elevation of others.
Principle Ten: All persons ought to dedicate themselves necessarily for the social good and the well being of all, subordinating their personal interest, while the individual is free to enjoy freedom of action for the individual well being.
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Swami Dayanand was a rigid propounder of the Vedas. In the 1857 edition of of Sattarth Prakash he had advocated:
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