Are Animals Sentient?

Here is a passage from John Rodman's classic essay "The Dolphin Papers," The North American Review 259 (spring 1974): 13-26, at 24:

St. Augustine [354-430] had long ago decided that beasts were incapable of suffering pain, because otherwise God would be unjust. (Assume that beasts share neither in original sin nor in eternal life; then for them to suffer pain seems to contradict the principle that "God being just, no being suffers undeservedly"; therefore, animals must not be thought to suffer pain.)

As I interpret the argument, it goes like this:

1. If (a) animals are sentient (i.e., capable of suffering), (b) animals are innocent (i.e., not afflicted by original sin), and (c) animals lack immortal souls, then there is undeserved suffering.

2. If there is undeserved suffering, then God is unjust.

Therefore,

3. If (a) animals are sentient, (b) animals are innocent, and (c) animals lack immortal souls, then God is unjust (from 1 and 2, hypothetical syllogism).

4. God is not unjust.

Therefore,

5. It is not the case that [(a) animals are sentient, (b) animals are innocent, and (c) animals lack immortal souls] (from 3 and 4, modus tollens).

Therefore,

6. Either (a) animals are not sentient, (b) animals are not innocent, or (c) animals have immortal souls (from 5, DeMorgan's theorem).

7. Animals are innocent.

8. Animals lack immortal souls.

Therefore,

9. Animals are not sentient (from 6, 7, and 8, disjunctive syllogism).

The argument is valid, so everybody must either reject 1, reject 2, reject 4, reject 7, reject 8, or accept 9. Augustine accepts 9. I reject 4, which falsely presupposes that God exists. How do you respond?

Addendum: I read Rodman's essay for the first time on 18 January 1981, when I was 23 years old and in my second year of law school. It has influenced me more than almost anything else I have read. If you'd like a PDF version of it, let me know.