"And, in defense of (1), Howard-Snyder gives the following sub-argument:
i. If objective consequentialism is true, then, of all those acts that
she can perform, she ought to perform the one that would produce the best
consequences.
ii. Beating Karpov is an act that she can perform. After all, there is a
series of moves, each of which she can perform, that would result in her
beating Karpov.
iii. Beating Karpov is, of all the acts that she can perform, the one
that would produce the best consequences.
iv. Therefore, if objective consequentialism is true, then she ought to
beat Karpov.
But, as Moore points out, (III) and (ii) contradict each other, and
Howard-Snyder cannot have it both ways. She cannot say that she both can
and cannot beat Karpov in the same sense."
"It seems important, then, to disambiguate two senses of ‘can’, for it
seems that in one sense Howard-Snyder can beat Karpov and in another
sense she cannot. Now Moore suggests that the sense in which she can beat
Karpov is the sense in which it is physically possible for her to do so.
He says, “Her beating Karpov is consistent with the physical laws of
nature. Call this sense, ‘can1’”. But this seems to conflict with
determinism. If determinism is true, then it may well be that her beating
Karpov is inconsistent with the physical laws of nature. It is
preferable, I think, to remain neutral as to whether the sense of ‘can’
under which she can beat Karpov is compatible with determinism. So let us
say, then, that there is a sense of ‘can’ under which Howard-Snyder can
beat Karpov, Tiger Woods can make a hole-in-one, and I can publish in the
Philosophical Review even though, in none of these cases, is this
something that is under the agent’s control in the sense explained in (I)
above. Let’s call this sense, ‘can1’, and let’s call the sense of can
given in (I) above, ‘can2’."
"It’s clear, then, that if the foregoing interpretation of Howard-Snyder
is correct, then Howard-Snyder is illegitimately equivocating between
these two senses of can.
a. If objective consequentialism is true, then (since Howard-Snyder can1
beat Karpov) she ought to beat him.
b. But Howard-Snyder cannot2 beat Karpov.
c. ‘Ought’ implies ‘can2’: if an agent cannot2 do something, then it’s
not true that she ought to do it.
b. [sic] Therefore, it’s not true that Howard-Snyder ought to beat
Karpov. [from (b) and (c)]
e. Therefore, objective consequentialism is false. [from (a) and (d)]"
"This argument doesn’t commit the fallacy of equivocation, so it is
valid. But, as Moore argues, we should reject (c). If objective
consequentialism is to be formulated in terms of can1, then so should the
ought-implies-can principle. Arguably, ‘can1’, not ‘can2’, is the ‘can’
of ordinary language, and we should formulate the ought-implies-can
principle in term of the ‘can’ of ordinary language, for the ought-
implies-can principle is justified by appeal to ordinary language. We
would not say that when Tiger Woods sinks a hole-in-one, he does
something he cannot do. Yet sinking a hole-in-one is not something he
can2 do."