1. It makes sin (disobedience) and obedience impersonal.
First, it is an impersonal, institutional idea, derived equally from the Church discipline, the Wergeld, and feudalism. If the law be regarded as impersonal, and the debt of man as well, then any one may render satisfaction. But justice, or rather righteousness, is God's nature, and law is the expression of His character, of Himself. He demands man's obedience, and that is what man owes. Christ's obedience cannot be accepted in place of ours, because it is ours which is wanted. The obedience which we failed to render cannot be offered by any one else, so as to make up the deficiency; because obedience is personal, and nothing can be done with the deficiency but to pardon it or else let it work its due punishment. One who is mystically united with us, as our Head, our Sponsor, our Representative, may offer His perfect obedience as the pledge of our own, as the response of humanity to the requirements of God. But God can be satisfied with nothing less than righteousness, and not even with that from any other than the one who lacks it and of whom He asks it (pp. 182-83).
2. It fails to distinguish between a material and a moral debt.
Again, the idea of substitution fails to distinguish between a material and a moral debt. The difference between a pecuniary and an ethical obligation is now generally recognised, because the Anselmic theory of a judicial process that would nowadays be called civil has given way to the analogy of ciiminal proceedings. But the fundamental point remains untouched, and the following admissions, chiefly by believers in satisfaction, may be applied to Anselm's satisfaction by substitution. Archbishop Magee says: "Neither guilt nor punishment can be conceived, but with reference to consciousness which cannot be transferred" [Discourses and Dissertations on the Scriptural Doctrines of Atonement, p. 197]. Anselm does not teach that Christ bore our punishment, though he uses the idea of guilt as indicating our exposure to penalty; it is in this connection that we may claim Magee's support (p. 183).3. It is based on a fiction and is unjust.
... Anselm has ignored the significance of a moral debt and treated it as simply material, as so external to the person as to permit of a transfer of the duty of obedience (p. 186).
The idea of literal substitution is really a survival of folk-faith, where continually we see the disposition of men to shift upon another the results of their sin. But it cannot for a moment be considered as literal, because it is an utterly fictitious proceeding, and confusing to the moral sense. It makes God violate the very justice which is said to demand satisfaction, because it makes Him satisfied with an obedience as ours which is not ours. This is a double offence against justice: it foregoes the claim of obedience upon the one who owes it, and it accepts a substitute from one who does not owe it (p. 186).