Lactantius appears to be working with the metaphysical categories of Stoic philosophy (i.e. relative dispositions) when he attempts to explain the ontological relationship between the Father and the Son. Father and Son are correlative concepts. That is, one cannot be deemed a father without a son nor can a fetus experience birth as a son unless a father “creates” him. On the other hand, there is a sense in which both father and son create one another, according to Lactantius. The result of this relational creative process is that father and son come to have “one and the same mind in each, one and the same spirit and one and the same substance.” Nevertheless, the difference between the two dispositional relations is that the Father is comparable to a spring “in full flow,” whereas the Son is analogous to a flowing stream that originates from the primordial source of divinity. Furthermore, the Father is akin to the Sun; Christ, on the other hand, is comparable to “a ray projected from it.” Lactantius seems to emphasize a moral union that obtains between the Father and Son: the Son is one with his Father in that he is loyal and highly esteemed by the Father (Divinae institutiones 4.29.5).
Lactantius not only appeals to illustrations concerning the river and sun, however, but he also invokes such examples as the relationship between a voice and mouth or virtue and the body: “Equally, a voice cannot be divorced from a mouth, nor can virtue or an act of virtue be detached from a body.” A more “immediate example” that explains the unity of the Son and Father is that of a compassionate father appointing his son over his household. Technically, ancient civil law in Rome only allowed for one master of the household; Roman law specified that fathers were the sole masters of their individual households. Nevertheless, the law did allow fathers to grant sons “the name and power of master,” under the authority of the father. Hence, while an ancient Roman father might permit his son to be dominus domūs, according to civil law, there was only “one house and one master of it.” A father and son were thus one from a legal standpoint. It is clear that Lactantius relies on principles from civil law obtaining in antiquity to illustrate the Father and Son’s moral oneness and their putative ontological relationship. He also draws a parallel between the Godhead represented in two persons and Roman law, whereby a father could enable his son “to assume in a legal sense his father’s personality.” Lactantius is probably thinking of the Roman paterfamilias when he argues that God is master and father of the universal household that he allows the Son to govern (Divinae institutiones 4.29.8). Figuratively speaking, the Son only becomes sui juris following a legal ceremony of emancipation.
 DI 4.29.3.
 DI 4.29.4.
 DI 4.29.4.
 McGuckin appeals to DI 4.29.4 to substantiate his belief that there is development in Lactantian thought regarding the Father and Son. However, it does not seem prudent to read post-Nicene senses into the Lactantian formula, “una mens, una spiritus, una substantia.” While attempting to make an argument for catechetical development in the writings of Lactantius, McGuckin nevertheless concedes that the language of DI 4.29.4 “should not be pressed.” See “Christology of Lactantius,” 817.
 DI 4.29.5.
 DI 4.29.6-7.
 Bowen and Garnsey, Divine Institutes, 10. Compare Augustine’s use of dominus domūs in Confessiones 8.8.19.
 Lactantius is far from the Trinity, appearing to be more of a ditheist (Hagenbach, Textbook, 244). Hagenbach believes that the thought of Lactantius (Christologically speaking) is “wholly Arian” since the apologist compares Christ to an earthly son who shares all things with his father while dwelling in the father’s house (Textbook, 244). See Campenhausen, Fathers of the Church, 75-77 for information on a first and second God.
 Cruttwell, Literary History, 649.
 Cruttwell, 649.