However you construct your world it is done by way of the common sense and hence the source of a certain confidence in the intelligibility of your utterances no matter how strange or even perverse they might at first appear. How do you know this? How can you presume to be both entirely distinct and entirely general in this way? Isn't it a presumption often proved wrong in the application? Where one looks for communicative reason, kommunikative Rationalität, one, or another, generally ends up with le différend. There is difference in structure and difference in axioms - you know that the structure is the same because it is precisely this parity which enables you to discover the differences in starting points. Well, perhaps, but it is not clear how you would distinguish this higher level of difference, how mark these meta-differences in outlook, only that at some point common sense must be surrendered. There certainly are differences in structure, but structures do not differ wholesale, they are made up of parts and where some parts are common, others may be divergent. Some insight into this is possible. One structure may properly contain another structure, but since their function is precisely to simulate each other, to make models of other ways of knowing, the contained will never know or admit itself as contained. Reflection on the structure of your own knowing nevertheless has a kind of certainty beyond any that belongs to the content of knowing. It is not the philosophical differences but the fact that you participate in the kind of being for which these differences are possible. It is not your world but the world's you.