At base, there are only two worldviews, Christianity and non-Christianity. There are numerous instances of texts of Scripture which give rise to this understanding of worldviews. Of course, within the realm of non-Christian thought there are many manifestations of the non-Christian worldview. For example, Islam and agnosticism are two different manifestations of the rejection of the Christian worldview. These manifestations are what people typically refer to when speaking of worldviews. This may serve to raise some interesting discussions about the terms we use when describing the aforementioned entities, but for now we will set this issue aside.
A frequent objection to the presuppositional method of apologetics is that it does not take into account the necessity of answering questions concerning other religions as opposed to atheism. There is a small bit of truth in this only because presuppositionalist apologists have traditionally focused the vast majority of their energies upon going after the "atheist worldview". However, stating this is a long way from conceding that somehow presuppositionalism is inadequate to deal with "religious" manifestations of the non-Christian worldview. Such a concession is unnecessary not only due to its falsehood, but also because no other method is sufficient to take on the challenge of non-Christian religious worldviews. What other worldview would we stand upon? What do classical and evidentialist apologists, who speak of probability and hypotheses and "establishing some of the alleged attributes of a general concept of god" have to offer in terms of responding to religions that share the very doctrines they are supposedly able to establish through reason?
The point in bringing all of this up is to establish that we need not fear answering non-Christians of any type while standing upon our Christian worldview. We do not flee from religious sects, nor do we suddenly turn about and cease to utilize our sound methodology. Rather, we follow the same procedure of showing that our God of the Christian Scriptures alone provides the preconditions for any intelligibility whatsoever and that all manifestations of the suppression of the truth of God fail to render anything intelligible upon their own presuppositions.
Recently I was asked how I might approach the ancient religion of Zoroastrianism. Since there are only just over 100,000 Zoroastrians in the world, I presume that the question was asked primarily as a means to uncover a specific example of how to deal with false religions via presuppositionalist methodology. There are only a handful of geographical locations in the world where one might come across someone who adheres to Zoroastrianism. Such questions should nevertheless be asked in order to see our apologetic in action in more specific contexts than what is offered in most current literature on the subject. Thus, the question and answer have practical merit. Aside from this it is worth noting that Zoroastrianism has long been taught about as being strangely and strongly parallel to Judaism and Christianity and as predating the latter two religions. These assertions are sufficient to raise questions and doubts in the minds of some believers. Indeed, raising doubts would seem to be the intention of many texts and teachers of this subject as it is with so many other secular philosophies imposed upon students through allegedly innocent, neutral academics.
So how does one deal with the challenges presented by Zoroastrianism? The general answer is that we approach it in the same way we approach any other version of non-Christianity. We shall set Christianity as a whole over against Zoroastrianism and see which is intelligible on its own terms. This procedure will involve a study of the concepts of revelation, God, humanity, sin, redemption, etc. The specific answer to the original question is the content of the next few installations pertaining to this subject. I hope to see you there.