Complex sentence: He regarded the Caliphate as a symbol of Islamic unity, and believed that this unity must be based on justice and solidarity, not on oppression and subjugation; and that it should mean fraternity and cooperation among Muslims, not despotism and exploitation.
Split into simpler sentences: He regarded the Caliphate as a symbol of "Islamic" unity and believed that this unity must be based on justice and solidarity, not on oppression and subjugation. It should mean fraternity and cooperation among Muslims, not despotism and exploitation.