大方廣佛華嚴經隨疏演義鈔 14.37

14.37

疏「互用皆通」者，謂不壞性相，則理法界，性義名界。若事法界，分義名界。若性相交徹，相既即性，分即名性，性即相故。無分即分，故言互通。

Regarding "Interchangeable usage is universally valid": this means that without destroying nature and characteristic, in the dharmadhātu of principle, the meaning of "nature" is termed "dhātu" (realm); in the dharmadhātu of phenomena, the meaning of "division" is termed "dhātu." If nature and characteristic interpenetrate, since characteristics are identical to nature, division is called nature; and since nature is identical to characteristics, non-division is division. Hence it says "interchangeable usage is universally valid."