One could answer a strict no on this question.Yes one could argue that religion is religion and if you do not believe you are neither this nor the other, but I don’t think it is that easy to escape your ethnic and religious context even if you stop believing.
A person is born into the Jewish faith.Judaism is inherited from the mother's side. Their belief is that God chose the Jewish people to be his people and therefore they can not escape being Jews even if some have become secularized and others have become atheists. If God exists he has treated the Jewish people very badly over the centuries and this can be the reason why some of them have lost their faith. Others have lost faith because they need evidence and as there is no evidence that will hold up scientifically they can not believe. This is the same for all religions remember religion is a belief.
Jesus (Isa) was also a JewIt was only after his death, or after he vanished if we take the Muslim point of view, that they began to organize the religion called Christianity. They had a meeting and decided that this was something new and all who wanted to join should be welcome, not only Jews. Jesus talked equally to both men and women and some researchers argue that Mary Magdalene had a prominent role as one of Jesus disciples. Unfortunately this provoked the men who over time greatly dimmed her actuell role.
Around 600 years later Mohammed had his first revelations. He reformed very much that was wrong at that time and in the society in which he lived. He tried to get people to think about the poor. He himself had experiences of being poor and of loosing his parents at an early age. He wanted to create harmony between the tribes. Harmony makes it easier to trade. He used a lot of Jewish texts and rituals to accomplish this. He wanted to raise the morale standards and unite the community in Mecca, which in addition to Judaism and Christianity also was greatly influenced by polytheism. The evil of polytheism has often been greatly exaggerated in Islam. Yes there were some promiscuity but there were also elements of asceticism and celibacy.
Jesus as GodIf you believe that God came down to earth in the shape and form of Jesus and you believe the love that Jesus preached and that Jesus conquered death through the resurrection then that makes you a Christian and you can join the faith by being baptised. If you are born into the faith you are usually baptized as an infant and as a teenager you can strengthen your faith by becoming confirmed. There are many different forms of Christianity, there are Orthodox, Catholic, Protestant, Coptic and many others just like there are different forms of Islam in different parts of the world.
IslamIf you believe the love that Jesus preached and that he was a very important prophet born by the virgin Mary, and you don’t believe in the holy trinity because only God is God. And if you believe that Mohammed was Gods last prophet and that the Koran is Gods final words then you need to speak it out loud preforming a shahada and become a Muslim. If you are born into a Muslim family you learn from your family and as a teenager you can strengthen your faith by performing a shahada.
SwedenIn Sweden we have been Christian Protestants since the 16th century. The king wanted to become the head over the church so he could have access over the church wealth and use it to pay his debts. The church and the stat have been walking hand in hand until their divorce on 1st of January 2000. The church has had a strong influence on the Swedes in all aspects of life over the centuries. Reading was important for Protestantism. Their idea was that everyone should be able to read God's words and by doing so every one should be able to believe and se the logic in the Christian faith. This is why illiteracy is nearly obliterated in Sweden. The thought seems to have back fired. According to a Gallup poll from 2009, Estonia is the least religious country in the world closely followed by Sweden where there are only 17 percent who said that religion is an important part of daily life. Attributed to this, you will find churches everywhere and worship services are celebrated with only a handful of participants. Despite the failure of religious practice, people in Sweden are very conscientious and honest and they will turn to the church in times of great sorrow and major disasters. Swedes celebrate Christmas because it's a family occasion and sometimes the only opportunity to meet the family and experience childhood memories. Some atheists even confirm themselves for traditional reasons. Easter is celebrated less frequently but is still considered a major holiday which employers have to pay extra for. In Sweden you start to study religion, and this means all the five major religions Hinduism, Judaism, Buddhism, Christianity and Islam and some natural religions when you are around 10 years old and up throughout high school. This education is compulsory and you can not deselect it.
Religion in a contextThe various religions have different regions where they are prevalent. The communities have ages of very old traditions. This has shaped the various societies and their laws. The divine was obvious in both the Bible and the Koran and was seen as an absolute truths which could not be contradicted. As a Muslim, your faith in God is just as important as it is in Christianity, but society is also formed around you. Spending time within a religious culture helps to keep you on track. Reading has been important in Judaism, Christianity and Islam, but if you can read one text it means that you can read other texts and with knowledge comes questions about old truths. Societies evolve and change. Being an atheist or an agnostic does not mean that you are evil or feel the need and want to live a promiscuous life. It is more about that you feel in your heart and what is the right believe for you. Sadly there are as much prejudices about atheists than there is about any other believes. People who believein in God feel that they have the right to tell you what will happen to you after you die, as if they know.
A belief is a beliefCan we be Christians or Muslims, and at the same time, secular, agnostic or even atheists? Faith-wise, we can not but on the other hand your faith is personal and something that is a matter between you and your God. Have you lost your faith well then you have. This does not mean you need to refrain from staying with your loved ones or that you may not participate in traditional ceremonies and it does not mean you should not dress in hijab if you have a cense of belonging and want to wear it. Often women want to wear the hijab just because it has become stigmatized. The interesting thing is that you often see young women in very tight clothes wearing hijab. Loose-fitting clothes have never been the topic off discussion and therefore they do not feel the need to wear them. The question is how much society around you forces you into the ranks. This is the hardest part and that is why many keep a good face, even if in their hearts they do not believe. The collective is more important than the individual in most Muslim and Christian societies. Religion is about being together and feeling a bond with family, friends and the surrounding society. Not all people are prepared to loos this and why should they. But we can not live in the past, we use medical developments that did not exist in Jesus and Muhamed time. We use technologi that did not exist in Jesus and Muhamed time. Why is it wrong to use results from gender research? There will probably come a time when Muslim and Christian society will have to face up to Muslim and Christian feminists and what they demand, because if they do not I think Islam and Christianaty will be in for a rocky future.