A look at the opinions of the experts about the signification extent of rational proofs of the Quran's undistortability

There are various proofs for the undistortability of the Quran some of which are rational and some others narrational.
Narrational proofs deny all kinds of distortions, such as addition or omission or displacement; but there are disagreements about the domain of rational signification on the immunity of the Quran.
The author of this paper has studied, through descriptive-analytical method the views of the experts in this field and has come to this conclusion that the reason has a clear indication for undistortability of the Quran, in term of addition or interpolation spoiling the miraculous nature of the Quran.
But in order to prove undistortability of the Quran, in terms of diminution, the rational reason alone is not effective so we should rely for this purpose on narrations.