Since the personal union cannot be perfect and permeant (perichoristic) without the participation of properties, the communication of attributes (communicatio idiomatum) of the two natures in Christ is the necessary result of the personal union. When the Son of God assumed into His person true human nature, He assumed also the properties which belong to human nature (to be a creature, to be born, to suffer, die, ascend and descend, move about, etc.). All who deny the communication of attributes must deny also the personal union, or the paramount mystery that the Word was made flesh.
Hollaz describes the communication of attributes (communicatio idiomatum) thus: “The communication of attributes is the true and real participation of the properties of the divine and human natures resulting from the personal union in Christ, the God-man, who is denominated from either or both natures.” (Doctr. Theol., p. 321.)
By the term properties (ἰδιώματα, propria) , which is here used in its wider sense, we understand not only the natural properties themselves, but also what they do and what they suffer (ἐνεργήματαa καὶ ἀποτελέσματα, actiones et passiones) , by which the properties exert themselves (to create — to be created; to give life — to lose life).
While the idiomata of the two natures are attributed to the concrete of both natures (Christ — the God-man) or to the concrete of either of the two natures (God — the Son of Man), it does not follow from this that the properties of the one nature become those of the other (God is not mortal; man is not eternal); for by the personal union the two natures are not changed in substance, but each retains the idiomata essential or the idiomata natural to itself. (Doctr. Theol., p. 313.) Therefore it is only to the person that without further distinction the idiomata of the one or the other nature can be ascribed. This truth will be considered more fully later on.
When we speak of the “concrete of the divine nature” we mean such terms as God, Son of God, the λόγος, etc.; when we speak of the “concrete of the human nature,” we mean such terms as Man, Son of Man, Son of Mary, etc.; when we speak of the “concrete of the person,” or of both natures, we mean such terms as Christ, Messiah, Immanuel, etc., which properly signify the person consisting of both natures.
Although every truth that will be set forth under the head of “Communication of Attributes” is already embraced in the doctrine of the personal union, we nevertheless treat the teachings of Scripture on this score under three distinct heads in order that the doctrine of the communication of attributes may be perceived the more readily and the antithesis of errorists may be refuted the more efficiently. Accordingly we speak of Three Genera of the Communication of Attributes.