The ugly duckling (habarvazon ha’mechoar) thought all his life that he was a duck, until one day he looked into the lake and saw that he was actually a swan. So is he a swan or a duck?

The case of whether one is a Jew or not is -in my opinion- clear-cut. You either are technically a Jew or you are not. If you are not a technically a Jew then eating falafel and putting on tefilin daily will not make you Jewish. Religion is the only common aspect of Jewish people around the world. Whether one follows all, some or none of its laws is another matter.