My friend Matthew is a Muslim from Scotland. We regularly go to Büyükada together at the weekends and spend the afternoon on talking - often about religion and history. Matthew, 24, became a Muslim seven years ago in his home city Edinburgh.
He grew up in Scotland as a Catholic Christian, like his mother, but does not think of himself as a convert.
"There is only one God," he says. "We are all born with the knowledge of God and it's only our culture and environment that shapes us."
He had read a lot about the religion before becoming a Muslim. Then one day he met an ex-priest in a mosque in Edinburgh who spoke about the purity of the Koran.
"I always prayed to God, and Islam took the barriers away."
His friends joked about his decision and thought it was strange. His Catholic mother was uncomfortable with it, and still is, but their relationship remains close.
Matthew says this kind of decision is not uncommon in Scotland. He knows many other people who have done the same thing. It has made his life easier, he adds.
"It has helped me to think about things and make more informed decisions. It has brought me a lot of happiness and contentment and given me direction."
"Islam is a way of life that stresses the importance of God, who should be the main focus in our lives."
Matthew's father asked him why he hadn't become a Buddhist! His father, like me, is agnostic. This is different from an atheist, who does not believe in God or religion.
Agnostics are neither believers nor non-believers. They simply say they do not know and probably are not supposed to know.
A growing number of people is calling themselves agnostic, especially in the traditional Protestant Christian world.
"My dad believes religion does a lot of good in people's lives but he doesn't actually believe that there is a God," says Matthew. "He describes himself as an'agnostic humanist.' He would not say he is an atheist though."
Matthew studied Arabic with politics and history at university, specializing in Islamic and Jewish studies.
He later lived and studied in Syria, Egypt and Morocco and speaks the Arabic fluently.
He came to Turkey because he was interested in Ottoman history and thought it would be a good place to visit.
But he will be returning to Britain soon, as he is getting married in Bradford in August. His fiancée is an English high school teacher whose parents are from Pakistan. She is also a Muslim.