you are asking to defend secularism against lets say theocratic state... my answer would be that secularism is better because it places less obstacles for the society to progress and evolve forward - obstacles in a form of religious dogma that would strip people of their freedoms, freedoms to think and do - that the best of us (the inventors for example) need to push us all forward with their great inventions... and the theocratic state would sooner or later come to state when strong dogma will be pushed and it will stop any progress being made... it will be pushed because it could be pushed...because in theocratic state power structure it is possible to push for strong dogma... because strong dogma gives the theocratic ruler more power... because power corrupts and absolute power corrupts absolutely... thats why theocratic states would have the tendency to degenerate into totalitarian states that limits peoples lives more than its beneficial to anyone (except for the ruling class) - therefore secular state is better - secular state also has many challenges to stop various types of elitists oligarchs who are trying to usurp all the power and push for hard totalitarian regime, but at least the threat of church elitist oligarchs is dealt with.
Why do I think this is the tendency? Bacause I look at Islam's history. Its very important to remember the golden age of Islam - the age that gave us all the inventions, that pushed humanity forward so much. But every muslim must know why it stopped. Why the greatest most progressive leading culture of the world fell so so much behind when the golden age of Islam stopped. Because the church and the state were not separated. Because anti-science zealots clerics came to power. Bacause these prothets - the political leaders of culture that gave us astronomy and advanced mathematics - banned numbers and pronounced numbers to be devils worship. And time rolled back centuries at that moment in the islamic world - because theocracy state power structure allowed backwards evil men to came to power and oppress their people with strong religious dogma that destroyed everything that the great great men worked on for generations during the Islamic golden age.
This regression couldnt happen in secularist state, therefore the secularist state is better. As I said before such regression might occur in the secularist state for other reasons...maybe... but at least secularist state is safe from such regression appearing for religious reasons.
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