But why since our deductions to different arguments will be validated by our presuppositions? One cannot renounce them, even you mr philosophy.
well, the key issue here is probably bound up in the difference between our view points. I'm not reformed, and ultimately don't agree with the foundational presmises of presuppositional apologetics.
However, when talking to people, you also have to realize that most people are not terribly logical and they themselves probably don't fully understand the logical implications of their beliefs, or their presuppositions.
This is why so many people hold views that are ultimately inherently contradictory.
This is why Atheists often hold view points that ultimately require or depend upon theism. They don't really understand the logical implications of their own beliefs, so they beliefs which can be contradictory to their stated presuppositions.
I'm not sure if this is exactly where you were going, or where you were coming from, but the foundation of presuppositional apologetics is a reformed belief that the unsaved are compeltely incapable of understanding God's truth, because of their false presuppositions. Also it leans towards the idea that apologetics in a traditional sense is useless because ultimately no one can be saved by argumentation, but rather God predestines those who will be saved, and enlightens their minds etc.
The problem with this, from my view point, even allowing the basic reformed doctrines of predestination etc, is that it makes assumptions about how God will chose to work and how he will call the unsaved.
An unsaved person can not understand God's truth, however, you and your conversation with them may be the tool that God has chosen to enlighten them. Thus it is your duty to know how to speak to them.
going beyond that, presuppositional apologetics tends to have an indifferent view towards the unsaved. The problem is that we don't know who is predestined and who is not, thus we have no right to start judging who we have to care about and who we don't.
The approach of so many people in just viewing the unsaved as numbers, or notches on our belt, is ultimately uncarring, and people can usually tell whether you care about them or not, whether you have any basic level of respect for them, by whether or not you take the time to try and understand them... before telling them what they actually believe
