Aflaq's theories about society, economics, and politics, which are collectively known as Ba'athism, hold that the Arab world needs to be unified into one Arab Nation in order to achieve an advanced state of development. He was critical of both capitalism and communism, and critical of Karl Marx's view of dialectical materialism as the only truth. Ba'athist thought placed much emphasis on liberty and Arab socialism – a socialism with Arab characteristics, which was not part of the international socialist movement as defined by the West. Aflaq believed in the separation of state and religion, and was a strong believer in secularisation, but was against atheism. Although a Christian, he believed Islam to be proof of "Arab genius". In the aftermath of the 1966 Ba'ath Party split, the Syrian-led Ba'ath Party accused Aflaq of stealing al-Arsuzi's ideas, and called him a "thief". The Iraqi-led Ba'ath Party rejects this, and does not believe that al-Arsuzi contributed to Ba'athist thought.