GAMAL AL-BANNA is 85, and for much of his life he has been overshadowed by his famous brother, Sheik Hassan al-Banna, the founder of the Muslim Brotherhood, the Islamist political party and antecedent of a host of militant Islamist organizations, from Al Qaeda to Hamas.

That seems to have suited him just fine, though. He liked to write, read and think. His sister left him a lot of money, and so for decades, that is exactly how he spent his days.

His bedroom is at one end of a dusty old apartment on a chaotic street in the center of the city. At the other end is his office, his desk piled high with papers. In between are books — some 30,000 of them — arranged neatly on floor-to-ceiling shelves. One section is devoted to the 100 or so books he has written and translated over the course of his lifetime.

But Mr. Banna is no longer living in his brother’s shadow. And, like the organization his brother founded, the younger Mr. Banna is no friend of the establishment, but for quite a different reason. He is a liberal thinker, a man who would like to see Islamic values and practices interpreted in the context of modern times. Egypt’s gatekeepers of religious values, the government-appointed and self-appointed arbiters of God’s word, condemn, dismiss and dispute what he says. They have also banned at least one of his books.

“Gamal al-Banna has opinions that fall outside the scope of religion,” said Sheik Omar el-Deeb, deputy in charge of Al Azhar, the centuries-old seat of Islamic learning in Cairo. “The people, of course, oppose anybody who talks about things that violate religion.”

Mr. Banna likes to wear a blue collarless suit, buttoned to the very top. He prefers sandals to shoes, and wears his thin, wiry white hair swept back. He is often laughing, a kind of knowing chuckle that seems to say he knows better, by virtue of his age and experience.

He doesn’t press his ideas, does not try to wage a contest with the institution of Al Azhar, but instead takes the long-term view, hoping to plant a few seeds that will, in time, take root and spread. He recognizes that, at the moment, the other side is winning the contest of ideas in Egypt, and the region.

“If religion was correctly understood, it would be a power of liberation,” Mr. Banna said. “But it is misunderstood, and so it is driving us backward.”

The views alleged to fall outside religion include those on women: They are not required to wear a veil, as most do in Egypt, Mr. Banna believes; they should not be forced to undergo genital cutting, as most do now in Egypt; and they should be allowed to lead men in prayer, which is forbidden in Egypt.

“My idea is that man is the aim of religion, and religion only a means,” said Mr. Banna. “What is prevalent today is the opposite.”