Thank you very much for your reply, dear Jawaid.
I remember in one of the books of Allama Parwez, he wrote that human has no conscience and (without a standard criterion) he/she only justifies his desires with the intellect .
Dr. Shabbir in QXP also mentions the following statement:
"conscience is only the "internalized society", a mental
reflection of the values prevalent in a given environment."
Slavery was allowable in the past, some Arabs killed their daughters, some local nations had accepted relationship between very close relatives etc, if human can distinguish right from wrong by only his intellect, then why did they were ok with those works.
What is your opinion, dear Jawaid?