Abstract Terminology is Necessary

Arcana Coelestia 4585:4-5 explains why the Heavenly Doctrines need to use abstract terms like "natural," "interior," and "rational."

These things have indeed already been occasionally unfolded, nevertheless they who have previously had no idea about them in consequence of having no desire to know the things of eternal life, find it impossible to have any such idea. Such people say, "What is the internal man? Is it possible that it can be distinct from the external? What is the natural, and the rational? Are they not one? Moreover, What is the spiritual, and the celestial? Is not this a new distinction? We have heard of the spiritual, but that the celestial is something else we have not heard." ....

Nevertheless as they are such things as are contained in the internal sense of the Word, and these cannot be explained without adequate terms, and we have no terms more adequate for expressing exterior things than the term natural, for interior things than the term rational, for those things which are of truth the term spiritual, and those which are of good the term celestial, it is absolutely necessary to make use of these terms, for without terms adapted to the subject nothing can be described.