Human rights are conceived as universal entitlements that all humans possess merely due to being human. However, there is no consensus on what specifically should be considered a human right. The concept of rights has existed throughout history but the modern notion of universal human rights is a relatively recent development originating from European history in the 16th century. Major developments in philosophy and documents like the US Declaration of Independence established certain legal rights, and human rights became a central concern regarding issues like slavery in the 19th century. The World Wars were a driving force behind the modern development of human rights instruments and bodies like the UN.