This chapter begins the more speculative part of the book. It responds to two objections to the instrument doctrine. The first objection is that a person cannot use a nature distinct from him as his instrument, even a divine person, because the created nature would lack some necessary feature for it to exist concretely. With the help of John Duns Scotus’s theology of the hypostatic union, the chapter argues that Christ’s humanity can be an instrument of his person because created personality is an extrinsic feature to the constitution of human nature. If Scotus is right, then a divine person can use a really distinct human nature as his instrument without any loss to the fullness of his humanity. The second objection argued that the instrument doctrine amounts to nothing other than the attribution of secondary causality to Christ’s humanity. The chapter argues that the hypostatic union means that the actions of Christ in the flesh are irreducibly distinct from ours, belonging as they do to a divine person.

Chapter seven addresses the difficulty of the theological interpretation of evolutionary biology in delineating a precise account of the concurrence of divine and contingent causes engaged in speciation. Invoking Aquinas’s famous distinction between God’s primary and principal causation and the secondary and instrumental causation of creatures, a constructive model of the concurrence of divine and natural causes in evolutionary transformations is offered.