The act of converting people to one's own religion and tradition is as old as humans when they began to organize themselves into communities and lived in the presence of 'other' communities. In olden times it was pretty straightforward - you either killed every other, or at least the males, so that the other women could bear your own children, or at least you made slaves of the other and forced migration on them, ensuring distance from their own, and thus the other was masterfully eliminated or sublated. But this swallowing up of the other brought about ontological changes to the self (within whom the other continues to live, quite literally) which was not often acknowledged. In our modern time, with increase in sophistication and tact, this form of brute power is reserved only for epochal wars or for situations where none see, however, in regular modes of living, hard power has been traded for soft power. Now it is not the guns but the goodies that power produces that are used as instruments to convert the other into one's own - education, economics and politics are three key modes of conversion. If we take education as an example, how is it used as a means of conversion? The Latin ēducātiō means 'a breeding, a bringing up, a rearing'. Different communities possess not only different methods but also different knowledge and skills in and through which the younger ones are bred or brought up or reared. However, with the use of soft power, a particular powerful tradition's knowledge and skills are (a) first of all affirmed to be universal and beneficial for all, (b) then, it is taken to the other as a goody (often with a bit of force, through international policies, world bank, etc) that is beneficial to make the other as oneself. (c) This results in the other accepting the powerful tradition's education, thus one's own tradition is lost, often forever. The other is transformed, often without understanding the deep, irreparable implications their acceptance of the goody has brought with it.
But I would still like to argue that converting is a valid act, as long as it is mutual conversion in a dialogical encounter, in which the self and the other sit together and eat at the table. Another image can be that of mutual incarnation, mutual becoming of the other, so that both embody the other within themselves. It is only this swallowing of the other that creates a new self which entails both the self and the other.
