According to the report of the 9/11 Commission, Osama Bin Laden's world-view "relies heavily on the Egyptian writer Sayyid Qutb". Qutb was the foremost spokesperson of the Muslim Brotherhood, and his book Milestones is the best-known modern work of Islamic philosophy in the western world.
The younger Qutb went to school in Cairo and began his working life as an educationalist and literary critic, unbothered by political Islam. However, upon visiting the US in the late 1940s, he experienced racism, materialism and sexuality, and these triggered revulsion at the American way of life and a stronger devotion to Islam. (In fact, he considered even jazz as "primitive".) He joined the Muslim Brotherhood in the early 1950s.
Qutb was further hardened by the torture he suffered in prison following the Brotherhood's attempted assassination of Gamal Abdel Nasser in 1954. He saw the universe as torn between the forces of Islam and those of jahiliyah, the condition of ignorance that defines the pre-Islamic world. He believed that every single society in existence -- including all Muslim societies -- was in this state of jahiliyah and therefore worthy of jihad.
There is disagreement over the extent to which Qutb advocated the violence for which he is blamed. In his writings, he never openly advocates violence against individuals. However, his statement that all Muslim societies are in a state of apostasy, and worthy of jihad, directly influenced takfiri proponents such as Ayman al-Zawahiri of al-Qaeda. In 1966, following a further assassination plot by the Muslim Brotherhood, Qutb was hanged.
It has the right to destroy all obstacles in the form of institutions and traditions which limit man's freedom of choice. It does not attack individuals nor does it force them to accept its beliefs; it attacks institutions and traditions to release human beings from their poisonous influences, which distort human nature and which curtail human freedom.