Those things which are similar are often confused as being the same. This happens religiously (e.g. the concept the Allah and Yahweh are the same), sociologically (e.g. the idea that all Oriental cultures are the same), relationally (e.g. the idea that two brothers are the same), linguistically (e.g. the idea that ‘to’ and ‘too’ are the same) etc. It happens in almost every aspect of life and often represents either some fundamental misunderstanding of the fundamental nature of one or both objects, or some intentional attempt to make the two objects into one. One of the most common current areas in which this mistake is commonly made is in our understanding of religion.
I can remember the first time I found a book arguing that the gods of Judaism, Christianity, and Islam were all the same god, and therefore the three religions were the same religion. It was on the bargain rack at Barnes and Noble being sold for about $7 as a hardback. This idea is now very common, and many scholars put forth this idea as unquestionable truth. Of course, an in depth study of any of the three religions will quickly yield important differences between these deities. For instance, the Allah of the Qur’an does not offer mercy to his people. There is no concept of original sin in Islam, which means that there is not need for salvific mercy. One may actually be ‘good enough’ to earn paradise. The god of the Jews no longer demands sacrifices or dispenses punishment for sin (the nature of Judaism began some fundamental shifts after the destruction of the temple in 70 C.E.). Meanwhile, the god of Christianity both punishes sin and demands sacrifice (i.e. the crucifixion of Christ), and offers salvific mercy through that sacrifice. This is only one important difference.
The gods of Islam, Christianity, and Judaism are very similar in many ways, and certainly the god of Judaism up to circa 100 C.E. was identical with the god of Christianity. However, that similarity does not mean that these gods or that the religions that follow them are the same. In the same way, the fact that my brother and I have many similarities does not mean that we are the same person. We are related, as are Judaism, Christianity, and Islam, but we are not the same, and it would be a mistake to assume that we are, to expect the same behavior from us both, to anticipate the same reactions, or to assume the same problems.
Not too long ago I had a student in one of my world religions classes who was adamantly opposed to the idea that Christianity was in any way similar to Islam. He refused to accept that any similarities existed, because to him any similarity meant sameness. He thought that if he admitted that any similarities existed between these two religions, then he was saying that they were the same religion, and he was horrified at this idea. To this end he attempted to convince the class that Islam is a polytheistic religion closely based on the ancient Egyptian religion. He did not succeed, but he did succeed in alienating many of his fellow students, and in hurting his grade in the class. Not only this, but he will, in a real world, succeed in alienating any Muslim that he meets, and in lending a poor name to Christianity. All of this simply because he did not understand the difference between similarity and sameness.
When we assume that similar things are the same, we often make many mistakes. It is important to recognize differences, but also to recognize similarities, and understand that the two go hand in hand. Differences are not bad, but neither are similarities. They simply exist, and to function properly in the world we should recognize and accept their existence.