These are more of summary notes of certain sections of Turretin, vol. 2.
a composite union? This language is used both by the ancient fathers (rather unsoundly) and more recently by Reformed fathers. What the latter meant is that it is “composed rather of number than of parts properly so called” (II: 312) because many things (human and divine natures) numerically exist. The fact that the fathers speak of a composite person should put to rest the charge that the Reformed Christ is Nestorian.
The effects of the hypostatical union are twofold: some to the human nature and some to the person. To the former are ascribed the grace of eminence and habitual graces (graces that are still human qualities but magnified). What is communicated? The communication of attributes is an effect of the union whereby the properties of both natures are predicated of the person. It is a real communication with respect properly to the person. When Turretin speaks of abstract and concrete communications, the terms are to be understood this way: we are not asking whether there is a communication of a concrete human nature to the person of Christ. All sides acknowledge this. The question is whether there is an abstract communication of nature to nature.
If the divine essence is communicated to the human nature (ala Lutheranism and some expressions of Orthodoxy), then the following must hold:
A created thing becomes an uncreated thing.
The human nature is thus immense and finite.
Further, what is proper to one cannot be communicated to another; otherwise it would cease to be proper and become common to that which is communicated (324). Either all of the properties of the divine nature were communicated or none were, since the divine essence is simple. All of the properties of the Logos must be communicated or none are, since the Logos cannot be divided. Further, if on account of the union the divine properties are communicated to the flesh, then the properties of the flesh ought in turn to be communicated to the Logos (325). The union is reciprocal. However, they are unwilling to admit this. Further, if the union was made (the natures themselves and their properties remaining unconfounded and entire and distinct, as the Lutherans acknowledge) a communication of properties could not have been made in it. For what is communicated does not remain proper.