During his lifetime, Priestley's considerable scientific reputation rested on his invention of soda water, his writings on electricity, and his discovery of several "airs" (gases), the most famous being what Priestley dubbed "dephlogisticated air" (oxygen). . . .
Priestley's science was integral to his theology, and he consistently tried to fuse Enlightenment rationalism with Christian theism. In his metaphysical texts, Priestley attempted to combine theism, materialism, and determinism, a project that has been called "audacious and original". . . . Priestley, who strongly believed in the free and open exchange of ideas, advocated toleration and equal rights for religious Dissenters, which also led him to help found Unitarianism in England. The controversial nature of Priestley's publications combined with his outspoken support of the French Revolution aroused public and governmental suspicion; he was eventually forced to flee, in 1791, first to London, and then to the United States, after a mob burned down his home and church. He spent the last ten years of his life living in Northumberland County, Pennsylvania.
In 1782, he wrote a history of Christian doctrine which he entitled, A History of the Corruptions of Christianity . In his chapter on the history of the atonement he points out two significant objections to the Penal Substitutionary Theory of the Atonement (PST) as held by John Calvin:
It is evident, however, that Calvin believed the real descent of Christ into hell, not for the sake of preaching to the spirits in prison, or, as the primitive fathers understood it, to those who died under the old dispensation, but that he might there suffer the proper torments of the damned, and bear the wrath of God that had been merited by the sins of men. Yet he says, "God was not really angry with Christ, though he made him bear all the effects of his anger." He would certainly, however, have been the proper object of God's anger, if, as he maintains, "the stain (that is the guilt) as well as the punishment of sin, was laid upon him, so that it ceased to be imputed to men." If God was neither displeased with men because their guilt was transferred to Christ, nor with Christ to whom it was transferred, what was the object of his anger, and how was his justice really satisfied ?
A more difficult question, and to which it is impossible that any satisfactory answer should be given, is, how the sufferings of Christ can be deemed infinite, so as to make atonement for sins of infinite magnitude, when the divine nature of Christ, to which alone infinity belongs, is impassible, and his human nature could bear no more than that of any other man? It must be exceedingly difficult to conceive how any supposed union of the two natures can be of any avail in this case, unless, in consequence of that union, the divine nature had borne some share of the sufferings, which the scheme requires to be infinite, and this idea is justly disclaimed as impious. Osiander the Lutheran maintained that Christ, as man, was obliged to obey the law of God himself, and therefore that he made expiation for sin as God; but Stancarus, another Lutheran divine, in opposition to him, maintained that the office of mediator belonged to Christ as man only. Both these opinions, this writer says, are dangerous. This is not the only case in which we see men bewildering themselves, and puzzling others, by departing from the plain path of truth and common sense (pp. 89-90).
Priestly is, in my opinion, correct. (1) If God was not angry with Christ, then his wrath could not be focused on him even though the sins of the elect had been imputed to him. Thus, God's wrath was never poured out on sin and satisfaction for sin was not made. (2) If God cannot suffer, then only the human nature of Jesus suffered. If he suffered only as man, then his sufferings were not of infinite value and thus could not atone for the sins of mankind.