Moral Knowledge by Perception

MORAL KNOWLEDGE BY PERCEPTION1

Sarah McGrath

1. Introduction

On the face of it, some of our knowledge is of moral facts (for example, that

this promise should not be broken in these circumstances), and some of it is of

non-moral facts (for example, that the kettle has just boiled). But, some argue,

there is reason to believe that we do not, after all, know any moral facts.

For example, according to J. L.Mackie, if we hadmoral knowledge (‘‘if we were

aware of [objective values]’’), ‘‘it would have to be by some special faculty of moral

perceptionorintuition,utterlydifferentfromourordinarywaysofknowingeverything

else’’(1977,p.38).Butwehavenosuchspecialfaculty.So,wehavenomoralknowledge.

Following Mackie, let us distinguish two questions:

Q1: Assuming that we have moral knowledge, how do we have it?

Q2: Do we in fact have any moral knowledge?

In response to the first question, I argue that if we have moral knowledge, we

have some of it in the same way we have knowledge of our immediate environ-

ment: by perception. Many people think that this answer leads to moral skepti-

cism, because they think that we obviously cannot have moral knowledge by

perception. But I will argue that this is incorrect.

The plan for the paper is as follows. In Sections 2–4, I work up to my

answer to Q1 by considering rivals. In Section 5, I explain what marks my

answer to Q1 as a distinctive view, and defend it. In Section 6, I briefly discuss

how this answer to Q1 affects what we say in response to Q2.

2. Moral knowledge by an inference to the best explanation

2.1 Harman’s answer to Q1

The first chapter of Harman (1977) suggests an argument for moral skepti-

cism from which we can extract an answer to Q1.2 In brief, that answer is that if

we have moral knowledge, we get it in the same way we get scientific knowledge:

Philosophical Perspectives, 18, Ethics, 2004

by inference to the best explanation. It is plausible to interpret Harman as giving

this answer because he seems to conclude that we do not have any moral

knowledge from the fact that we do not get moral knowledge by inference to

the best explanation. Obviously, for this argument to go through, we need the

premise that if we have moral knowledge, we get it by inference to the best

explanation.3

The aim of this section is to clarify Harman’s answer on two points: the first

about what knowledge by inference to the best explanation involves, and the

other about what, if anything, a moral theory might explain. But first, let us

briefly review Harman’s argument for moral skepticism, to see how an answer to

Q1 can be extracted from it.

According to Harman, the reason that we do not have moral knowledge has

to do with the apparent lack of connection between observational evidence and

moral theory:

Observational evidence plays a part in science it does not appear to play in

ethics, because scientific principles can be justified ultimately by their role in

explaining observations…—by their explanatory role. Apparently, moral prin-

ciples cannot be justified in the same way…Conceived as an explanatory theory,

morality, unlike science, seems to be cut off from observation. (1977, p. 9)

The contrast Harman sees between the scientific and moral case can be brought

out by consideration of a pair of Harman’s examples (1977, p. 4, p. 8):

PROTON: A physicist sees a certain track in a bubble chamber and makes

the spontaneous judgment ‘‘There goes a proton’’. The fact that a proton

passed through the chamber, we may suppose, helps to explain the physicist’s

judgment. The proton produces the track, which in turn causes a certain

pattern of light to enter the physicist’s eye, which in turn causes the physicist

to make the judgment.

CAT: Jim rounds a corner and sees a group of young hoodlums pour gasoline

on a cat and ignite it. Jimmakes the spontaneous judgment ‘‘What the children

are doing is wrong’’.

Harman claims that CAT differs from PROTON in the following way:

[I]t would be reasonable to assume, perhaps, that the children really are pouring

gasoline on a cat and you are seeing them do it. But [there is no] obvious reason

to assume anything about ‘‘moral facts’’, such as that it really is wrong to set

the cat on fire…It would seem that all we need assume is that you have certain

more or less well articulated moral principles that are reflected in the judgments

you make, based on your moral sensibility. It seems to be completely irrelevant

to our explanation whether your intuitive immediate judgment is true or false.

(p. 7)

210 / Sarah McGrath

The contrast, then, is that in PROTON we do need to assume that there really is

a proton in the chamber in order to explain the physicist’s judgment. Whereas in

CAT, we do not need to assume that what the kids are doing really is wrong in

order to explain Jim’s judgment. And hence, Harman thinks, we don’t know

that what the kids are doing is wrong. This conclusion seems to depend on the

idea that if we knew, it would be by inference to the best explanation.

Someone might object to the suggestion that we come to know moral

hypotheses by inference to the best explanation as follows. If we have moral

knowledge, then many of our moral judgments that amount to knowledge will

be judgments that we form spontaneously, as is Jim’s judgment in CAT. That,

according to the objection, is inconsistent with the claim that we always know

moral facts by an inference—to the best explanation, or otherwise.

But this objection is misguided: it is consistent with Harman’s answer that a

moral agent forms her moral judgments spontaneously, without reflection. To

see this, it will be useful to consider a few more examples illustrating knowledge

by inference to the best explanation. First, consider:

CHEESE: On coming home from work, Erika notices that the cheese is

missing. She reasons as follows. ‘‘The cheese is missing. Could it be mice?

Maybe I left the cheese in the shop, or maybe…So, I have mice’’.

In this case, Erika knows she has mice in the following way. She considers a variety

of possible explanations of the fact that the cheese has been nibbled and concludes

that the most plausible among them is that there are mice. Let us call this a case of

explicit inference to the best explanation reasoning, because Erika actually goes

through the process of considering several possible explanations. Now consider:

DOOR: On arriving at work, Corinne sees that her co-worker’s door is

open. She spontaneously judges that Stephanie is in her office; she does not

consider a variety of possible explanations and conclude that one among

them is the most plausible.

In this case, the subject doesn’twonder aboutwhat the explanationmight be:Corinne

does not consider whether a burglar has broken in to Stephanie’s office, or whether

the wind has blown her door open, etc. It is true, however, that if you asked Corinne

how she knows that Stephanie is in, she could produce the inference to the best

explanation reasoning: that Stephanie’s being in best explains the fact that the door

is open. Let us call this a case of implicit inference to the best explanation reasoning.

Finally, consider

LABTECHNICIAN: Barbara the lab technician has been told that if she sees

a track in the bubble chamber, then there is a proton in the chamber. Barbara

sees a track, and thinks: ‘‘That’s one of those tracks, so there goes a proton’’.

Moral Knowledge by Perception / 211

In this case, there is no explicit or implicit inference to the best explanation reasoning.

Barbara does not consider a variety of explanations and conclude that one among

them was the most plausible; nor, had she considered rival explanations, could she

pick the one that was best. She does not understand the theory that explains the

track, and so could not produce the reasoning. Rather, Barbara’s knowledge that

there is a proton in the chamber relies in part on testimony: she was told that if there

is a track, then there is a proton. Still, Barbara’s belief that there is a proton in the

chamber ultimately rests on inference to the best explanation reasoning: her judg-

ment that there is a proton in the chamber counts as knowledge in part because some

scientist(s) somewhere performed inference to the best explanation reasoning.

So the justification for a judgment might be an inference to the best

explanation, even though the judgment is made spontaneously. Jim’s judgment

might be like Corinne’s: it might be a case of implicit inference to the best

explanation reasoning. Or, Jim’s judgment might be like Barbara’s: it might

rest on inference to the best explanation.

Now let us turn to the question of what, if anything, moral hypotheses

might explain. We said that Harman’s complaint about moral theory is that

there is an apparent lack of connection between observational evidence and

moral theory: theories are supposed to explain something. In CHEESE, the

thing to be explained was that the cheese was nibbled; in DOOR, it was that the

door was open; and in LAB TECHNICIAN, the explanandum was that there

was a track in the chamber. According to Harman, moral theory, like scientific

theory, ought to explain ‘‘observation.’’ But as Harman notes, ‘‘observation’’ is

ambiguous. ‘‘Observation’’ could refer to an act of observing, as in ‘‘Barbara

made her observation today at noon’’, or it could refer to the content of the act

of observing, as in ‘‘Barbara wrote her observation in her notebook.’’ This is the

Sellarsian ing/ed distinction: the distinction between the act of observing and the

content of what is observed. For clarity, let us use ‘‘judgment’’ for the act of

judging; ‘‘observation’’ for an observed fact.

Harman says that scientific, unlike moral principles, are justified ultimately

by their role in explaining judgments: unlike moral principles, ‘‘… scientific

principles can be justified ultimately by their role in explaining observations,

in the second sense of observation’’—where the second sense is the -ing sense

(1977, p. 9). So Harman’s answer to the question: ‘‘What if anything does a

moral theory purport to explain?’’ seems to be that if moral theory explains

anything, it explains the same thing scientific theory explains: judgments.

But that’s implausible about science: it is not at all obvious that certain

psychological events, namely scientists’ acts of judgment, ‘‘ultimately justify’’

scientific theories. For example, the theory of evolution is presumably justified

by its role in explaining the fossil record and the like; it is certainly not in

practice justified by its role in explaining psychological events occurring in the

minds of evolutionary biologists. Neither is it at all clear that the theory of

evolution could be justified—at any rate to the high degree to which it is actually

justified—by its role in explaining such psychological events.

212 / Sarah McGrath

The claim that scientific knowledge is not ultimately justified by inference to

the best explanation of judgments should not be confused with the extremely

plausible claim that if our beliefs in scientific theories are justified, then the truth

of those theories, at least in part, explains our beliefs. The latter claim does not

require that the plausibility of the theory derive from its success in explaining our

beliefs. But while that claim is surely correct, it is not a view about how we come

to know scientific theories. And the present suggestion is that if we come to

know moral theories, we come to know them in the same way that we come to

know scientific theories. (We will turn to the question of whether this necessary

condition can be pressed into service in a different argument for moral skepti-

cism in section 6 below.)

Returning to the idea that what a theory might explain is our judgments:

that idea is less implausible about moral theory than it is about science. For if a

moral theory explains anything, human judgments seem a good candidate as to

what it explains. As Thomson puts the point:

Nobody, I think, has the odd idea that the truth of a moral sentence might

directly explain the truth of a sentence reporting a purely physical phenomenon,

such as a bell’s ringing or a whistle’s blowing. (Thomson, in Harman and

Thomson 1996, p. 76)

Thomson thinks that if there are observations that moral hypotheses directly

explain, the most obvious candidates are observations about our moral

judgments. (A moral hypothesis, such as ‘‘Alice ought to ring the bell’’,

might well explain a purely physical phenomenon such as the bell’s ringing.

But it would do so indirectly, via Alice’s judgment that she ought to ring the

bell.) We might say something similar about color hypotheses—for instance

that limes are green—a comparison that Harman makes himself. The most

plausible candidates for what color hypotheses might directly explain are

facts about their psychological effects on us—our color experiences, or our

judgments about color. If the best candidates for moral explananda are facts

about our judgments, then if we have moral knowledge, we have it because

moral hypotheses best explain facts of this sort: ‘‘Jim judged that the

children were acting wrongly’’; ‘‘Most of us think that one ought to keep

one’s promises’’, etc.

Now that we have gotten clear on what, if anything, a moral theory might

explain, we can state the answer to Q1 that we have extracted from Harman

more precisely:

HA1: We know moral hypotheses by inference to the best explanation of

our moral judgments.

The next section argues that HA1–taken as an account of moral knowledge in

general—is incorrect.


2.2 Against HA1

Many people who want to resist Harman’s skeptical conclusion seem to

think that the most promising line of response is to accept HA1, and argue that

moral facts can be known by inference to the best explanation. According to this

response, moral facts play an explanatory role similar to the role that Harman

says that color facts play:

[I]t may be that the reference to the actual color of the object in an

explanation…can be replaced with talk about the physical characteristics

of the surface…but that would greatly complicate what is a simple and

easily understood explanation. That is why, even after we come to be able

to give explanations without referring to the actual colors of objects, we will

still assume that objects have actual colors…[and] will continue to refer to

the actual colors of objects in the explanations that we will in practice give.

(1977, p. 22)4

Here, Harman is explaining why his argument for moral skepticism does not

generalize to an argument for color skepticism. The passage suggests that if, in

practice, we find that a type of fact simplifies explanations of what we observe,

then facts of that type are explanatory enough to be known by inference to the

best explanation. So many people think that the crucial challenge posed by

Harman’s argument is to show that moral facts simplify—or otherwise

improve—explanations.5

But a more straightforward response is to deny HA1. Returning to the

case of color: no doubt color hypotheses do explain color judgments (and

experiences): that this snowball is white explains my spontaneous judgment

(and experience) that it is white. But I do not believe that this snowball is

white because that hypothesis would explain why I judge that snow is white,

or because that hypothesis would explain why it seems to me that this

snowball is white. Incidentally, neither do I believe that this snowball is

white because it’s being white would explain some other fact, say that it is

reflecting a lot of light across the visible spectrum. So if I know that this

snowball is white, it is not by inference to the best explanation—implicit,

explicit, or in the manner of the lab technician, above. Whether there

is some inference to the best explanation of our color judgments seems

irrelevant to the question of what justifies my belief that the snowball is

white.

One way to bring this out is to consider that where there is an inference to

the best explanation, we have the observations to be explained first, and then go

on to judge that hypothesis is true because it would best explain the observa-

tions. Let us return to the example of Jim’s judgment that what the children are

doing is wrong. If Jim knows that what the children are doing is wrong, then the

story about how he knows cannot be: the hypothesis

214 / Sarah McGrath

(1) What the kids are doing is wrong.

best explains this observation:

(2) Jim judges that what they are doing is wrong.

Jim can only reason that the truth of (1) is the best explanation of (2) after he

has made that judgment. But this would render his judgment some kind of lucky

guess: when he originally made the judgment, it was not justified by inference to

the best explanation. So Jim does not know (1) by inference to the best explana-

tion of (2), implicit or explicit. And neither, it seems, does Jim know (1) in the

manner of the lab technician: if he knows, he doesn’t know because someone

else reasoned that the best explanation of moral judgments is the truth of moral

hypotheses.6

A friend of the view that we know moral hypotheses by inference to the best

explanation might at this point reject HA1 and offer a different suggestion as to

what moral theories might explain. She might say that, pace Thomson, moral

facts explain phenomena other than our judgments. Sturgeon (1988), in addition

to offering examples in which a moral theory (allegedly) explains moral judg-

ments, offers a second kind of example in which a moral fact (allegedly) explains

something else: the fact that Hitler is depraved explains his deeds.

Here we can be brief. In Harman’s example of the children and the cat, it is

hard to see what the moral fact that the children are acting wrongly could

possibly explain, other than Jim’s judgment. So, if Jim’s knowledge that the

children are acting wrongly is founded on an inference to the best explanation, it

must be an inference to the best explanation of our moral judgments. But

Sturgeon’s second example is not an example of a moral fact explaining our

judgments: the fact that Hitler is depraved is supposed to explain death and

destruction. Hence, even if Sturgeon’s second example really is a case of a moral

fact explaining our observations, it cannot by itself support the view that moral

knowledge in general is supported by an inference to the best explanation.

3. Moral knowledge by inference from constituting non-moral facts

3.1 Thomson’s answer to Q1

So far I have argued that if we have moral knowledge, it is not solely by

inference to the best explanation. This section explains and then goes on to

criticize an alternative suggested by Thomson (1996). Thomson points out that

Harman seems to assume that we have evidence for a moral hypothesis only if

the truth of that moral hypothesis would explain observations, in the way that

the hypothesis that there is a proton in the bubble chamber would explain

the track in the bubble chamber. But, Thomson thinks, it is not true in general

that we have evidence for a hypothesis only if that hypothesis would explain


observations. For sometimes, the truth of p is evidence for the truth of q not

because the truth of q would explain the truth of p; rather, it is that the truth of

q would be explained by the truth of p. For example:

DICKENSON: We know that Dickenson will soon feel ill because we have

just seen him wolf down a dozen hamburgers. (Thomson, in Harman and

Thomson 1996, p. 92)

In this example, we have evidence that Dickenson will soon be ill (our hypothesis)

not because that would explain that Dickenson is wolfing down a dozen ham-

burgers (our observation); rather, we have evidence that he will soon be ill because

that is explained by the fact that he is wolfing down a dozen hamburgers.

Thomson’s idea is that our reasons to believe moral hypotheses are like

that: it isn’t that the truth of moral hypotheses would explain our observations;

rather it is that the observations would explain the hypotheses. This suggests to

Thomson that the answer to Q1 is that we have knowledge of moral hypotheses

because they are explained by observations (Thomson, in Harman and Thomson

1996, pp. 91–4). For example:

Suppose that Alice’s giving Bert a banana was her keeping her word when it

cost her a lot to do so and she could have got away with not doing so. That, it

seems plausible to think, would explain the truth of ‘‘Alice’s giving Bert a

banana was just’’. (p. 93)

In this particular example, our (non-moral) evidence is:

(NM) Alice’s giving Bert a banana was her keeping her word when it cost

her a lot to do so and she could have got away with not doing so.

(NM) explains (and so is evidence for):

(M) Alice’s giving Bert a banana was just.

Of course, this sort of explanation, of (M) by (NM), is not a causal explanation

(as was the explanation of the fact that Dickenson will soon be ill); (NM) is

supposed to metaphysically necessitate (strictly imply) (M). We might call it a

constitutive explanation. Still, it does seem to be an explanation of sorts. To return

to Thomson’s suggestion: the moral fact that what the children are doing is wrong

is explained by—metaphysically necessitated by—the observation that they are

causing the cat gratuitous pain. So Thomson’s answer to Q1 appears to be:

TA1: We have knowledge of moral hypotheses by inferring them from the

non-moral observations that metaphysically necessitate those moral

hypotheses.

216 / Sarah McGrath

Harman responds as follows (1996, p. 171). The moral skeptic doubts that

we have evidence for any moral facts, and requires, in order to be convinced, an

example in which a moral fact would explain a moral judgment. ‘‘Clearly, in the

context of a dispute as to whether actions like Alice’s constitute justice’’, the

claim that Alice’s giving Bert a banana in such-and-such circumstances explains

and is evidence for the conclusion that Alice’s giving Bert a banana was just ‘‘is

controversial and cannot show that there is evidence in favor of one moral

framework rather than another’’ (pp. 170–1). But while Harman’s response

would be relevant if the task were to convince the moral skeptic, who is not

prepared to take any moral facts for granted, it is not relevant for our purposes:

we are not trying to prove that Alice’s giving Bert a banana was just from

premises which even the moral skeptic would accept. At present, we are simply

trying to answer the question: if we have moral knowledge, how do we have it?

In this context, it is not disputed that actions like Alice’s are just.

3.2 Against TA1

Thomson’s proposal—or at least a proposal suggested by her remarks—is

that the answer to our first question is that we know that Alice’s giving Bert a

banana was just by inferring it from the non-moral fact that constitutes it, or on

which the moral fact supervenes. But this suggestion, like the previous one,

cannot be the whole story. To see this, consider:

(W) This glass contains water, so:

(O) This glass contains oxygen atoms.

Just as our non-moral evidence (NM) is sufficient but not necessary for (M),

(W) is sufficient but not necessary for (O). However, notice that you can’t

come to know (O) simply on the basis of knowing (W). In addition, you need

to know:

(W!O) If this glass contains water, then this glass contains oxygen atoms.

Someone who did not know (W!O) would be quite unjustified in concluding

(O) when she learns (W). Similarly, it appears, with (M): someone who merely

knows that Alice’s giving Bert a banana was her keeping her word when…is not

justified in concluding that Alice’s giving Bert a banana was just unless she also

knows:

(NM!M) If Alice’s giving Bert a banana was her keeping her word

when.…, then Alice’s giving Bert a banana was just.

So, on the present suggestion, the argument by which we can come to know (M)

has two premises, (NM) and (NM!M), both of which must be known. But now


it is clear that the proposal has only pushed the question back: how do we know

truths like (NM!M)? Thus while Thomson’s suggestion might be part of the

story about how we have moral knowledge, it can’t be the whole story: it needs

to be supplemented with an account of how we know the principles that take us

from non-moral observations to moral facts.

4. Moral knowledge from a priori moral principles and particular non-

moral facts

4.1 Thomson’s answer supplemented

We ended the last section with the question: how do we know truths like

(NM!M)? Since we may assume that (NM!M) is necessarily true if true at all,

one natural answer to the question is that we can know (NM!M) a priori. So

Thomson’s proposal might be supplemented: we know contingent moral truths

like (M) by inferring them from a priori moral principles—such as (NM!M)—

together with particular moral facts. This supplemented answer is:

TA1+: We know conditionals like (NM!M) above a priori. Moral know-

ledge about particular cases comes from combining these principles

with facts about the non-moral features of particular cases.

But TA1+ faces the following problem. We have supposed that ‘‘Thomson

conditionals’’ like (NM!M) are knowable a priori because they are necessary.

But (NM!M) is not necessary. To see this, suppose Bert is going to use the

banana in a crime, or that Alice has poisoned the banana, etc. In these circum-

stances, giving Bert the banana would not be just. We may grant that there is a

non-moral sentence, (NMþ), that metaphysically necessitates (M): that there is

a non-moral condition that is metaphysically sufficient for Alice’s giving Bert a

banana to be just. But (NMþ) will be very complicated: if Alice’s giving Bert a

banana was her keeping her word when it cost her a lot to do so, and she could

have got away with not doing so, and the banana was not poisoned, and Bert

was not planning to use the banana to rob a bank, and the banana was Alice’s to

give, and Bert was not trying to break his addiction to bananas, and it was not

the case that Alice could have used the banana to save a starving person…etc.,

etc., etc. It is not clear that we can state (NMþ!M), let alone know it a priori.

Alternatively, were we to add a ceteris paribus clause to (NM!M)—Alice’s

giving Bert a banana was just if, ceteris paribus, it was her keeping her word

when it cost her a lot to do so, and she could have got away with not doing so—

there is no guarantee that the ceteris paribus clause will not smuggle in some

moral conditions. In other words, holding all things equal might covertly be a

matter of holding equal some of the moral facts: for example, holding fixed that

there are not any extenuating circumstances that render giving Bert the banana

unjust.

218 / Sarah McGrath

In summary: in order to come to know particular moral facts from the non-

moral facts on which they supervene, we need to know some kind of principle

that connects the non-moral facts to the moral facts. This raises the question:

how do we know these principles? If answer is: we know them a priori, then the

connecting principles had better not be Thomson conditionals like (NM!M),

for those are not necessary. But necessary conditionals such as (NMþ!M) are

so complicated that it is implausible that we could know them at all, never mind

know them a priori. So we have not yet succeeded in supplementing Thomson’s

story in a way that yields a plausible answer to Q1.

4.2 A Moorean answer to Q1

Since the difficulty with TA1+ is that it is implausible that we can know

conditionals like (NMþ!M) a priori, a natural suggestion is that we modify the

view so that the relevant conditionals connecting non-moral features with moral

features are more general, and so more plausibly knowable a priori. Perhaps we

know one general overarching moral principle a priori, and come to have

knowledge about particular cases by applying this general principle on the

basis of non-moral features of particular cases.

As a representative example, consider consequentialism. Suppose some

version of consequentialism is knowable a priori. Let us put it in this schematic

form: x ought to do A iff A would maximize Fness. Then the idea is that we

come to know a particular moral fact, for example, that Alice ought to return

Bert’s banana, by inferring it from the non-moral fact that Alice’s returning the

banana would maximize Fness.

The problem with this account is that the best candidates for a priori

principles are those that substitute some moral (or evaluative) term for

‘‘Fness’’, and so applying such abstract principles will require empirical moral

(or evaluative) knowledge of the sort we are trying to explain. Moore’s version

of consequentialism can serve to illustrate:

That the assertion ‘I am morally bound to perform this action’ is identical with

the assertion ‘This action will produce the greatest possible amount of good in

the Universe’…is demonstrably certain. (1903, p. 197)

Assume for the sake of the argument that this statement of consequentialism is

‘‘demonstrably certain’’. Then in order to conclude that Alice ought to return

Bert’s banana, we need to know that Alice’s returning the banana will produce

the greatest possible amount of good in the universe. But, obviously, this is a

particular moral fact. But if it is a particular moral fact then we have again just

pushed the question back: how do we know that Alice’s returning the banana

will produce the greatest possible amount of good in the universe?

So suppose instead that the principle is: ‘‘An action is morally permissible if

and only if it maximizes human flourishing.’’ But how is ‘‘human flourishing’’ to


be explained? It is either to be explained in moral terms, or it is to be explained

non-moral terms. If it is to be explained in moral terms—for example, in terms

of possessing all the virtues—then in order to apply it to a particular case, we

will have to know particular moral facts about the case. So suppose instead

‘‘human flourishing’’ is explained in non-moral terms. Then the resulting prin-

ciple is not plausibly knowable a priori. To see this, suppose ‘‘human flourish-

ing’’ is explained in terms of what is non-morally good for humans. Knowing

that morality requires us to maximize that—food, shelter, friends, fulfilling

projects or whatever—would seem to require empirical knowledge. For whether

we ought to maximize what is non-morally good for humans seems to depend on

what is non-morally good for humans: if what is non-morally good for us turns

out to be that we torture other creatures for fun, morality would not require us

to maximize that.

Thus, in summary of sections 2–4: while it is perhaps true that some of

our moral knowledge is supported by an inference to the best explanation of

(non-moral) observations, and perhaps true that some of our moral knowledge

is supported by deductive inference from non-moral facts plus a priori princi-

ples, it is not plausible that all our moral knowledge could ultimately rest on

these two sources, either singly or in combination. In the next section, we will

consider the proposal that we acquire at least some of our moral knowledge by

perception.

5. Moral knowledge by perception

5.1 A first pass at the view

So far we have examined three answers to Q1. The first answer was: by

inference to the best explanation of our (non-moral) observations. The second

answer was: by inference from constituting non-moral facts. The third answer

was: by inference from a priori moral principles and particular non-moral facts.

I have not argued that the views we have discussed so far fail to account for any

of our moral knowledge. It might be that sometimes, we do get moral know-

ledge in the ways these theories say we do. My point is rather that none of these

views provides the whole story. In particular none provides the best account of

how we know an important and large class of moral facts: the facts about

particular cases.

In this section, let us turn to a fourth answer:

PA1: We have some moral knowledge by perceiving moral facts.

Many people think that on the face of it, this view is not at all plausible. They

think that it is implausible that we can perceive that, for example, torturing a cat

is wrong. But PA1 does not say that there is some dedicated organ of moral

perception, or that moral perception is just like perceiving colors and shapes, or

220 / Sarah McGrath

that the blind can’t perceive moral facts, or that we can perceive moral facts

without a lot of conceptual sophistication. We can perceive that other people are

in pain, that it’s time to water the plants, or that Fred told a joke. The

proponent of PA1 can say that moral perception is like that.

It might be useful here to compare the problem of whether we can perceive

moral facts with Hume’s problem of whether we can perceive that one thing

causes another. Famously Hume thought that we cannot: in searching for ‘‘that

primary impression’’ from which we get our idea of causation, Hume reasons

that we neither find it in the objects nor in the relations that we perceive. We

find the relations of contiguity and succession, but ‘‘can proceed no farther’’: we

find ‘‘only that the one body approaches the other; and that the motion of it

precedes that of the other, but without any sensible interval’’ (p. 77). We do not,

in particular, find an impression of a necessary connection.

Someone might say something similar about Jim. When he rounds the

corner, he sees only that there is gasoline, and that there is a cat, and that the

kids are pouring gasoline on the cat; there is not some additional fact—that

what the kids are doing is wrong—that Jim perceives. But surely Anscombe is

right when she complains, in ‘‘Causality and Determination’’ (1971) that we have

here an example of a philosopher who goes looking for something, concluding

that ‘‘all we find is such-and-such,’’ having decided in advance that we will not

find the thing sought. Anscombe points out that Hume might as well have

argued that, ‘‘neither do we perceive bodies, such as billiard balls…we find

only an impression of…a round white patch in our visual fields, etc.’’ (p. 61).

The point is just that so far, we have not been given some reason to think that

while we can perceive that one billiard ball approaches the other, or that some

kids ignite a cat, we cannot perceive that one billiard ball causes the other to

move, or that what the kids are doing is wrong.7

However, TA1 faces a problem, which can be brought out by discussion of a

recent paper defending it.

5.2 A problem

In their defense of a perceptual view of moral epistemology, Watkins and

Jolley develop what they take to be Aristotle’s idea that we get moral knowledge

by the exercise of ‘‘an intellectualized perceptual ability’’ (2002, p. 77). Knowing

that torturing cats for fun is wrong is like knowing that a particular wine has

hints of oak and strawberries: it is known by the exercise of perception aug-

mented by intellect (p. 77). If that is what moral perception is like, then seeing

that some particular action is wrong should be no more mysterious than

any other instances of perception that require some degree of sophistication,

training, or skill.

The problem with this view is not that it is false. On the contrary,

the problem—at least given our purposes here—is that it is obviously true.

That is, as explained so far, it is not really a rival view about moral knowledge.


Proponents of each of the views we have discussed so far can agree with PA1:

surely everyone who thinks that we have moral knowledge can agree that we

perceive the moral facts, in the way that Watkins and Jolley say that we do.

Harman, for example, in contrasting the scientific and moral cases, emphasizes

that the difference is not a difference with respect to whether we perceive the

facts in question:

… if you hold a moral view, whether it is held consciously or unconsciously, you

will be able to perceive rightness or wrongness, goodness or badness, justice or

injustice. There is no difference in this respect between moral propositions and

other theoretical propositions. (p. 5)

In other words, just as everyone should agree that the appropriately trained

physicist can perceive that there is a proton passing by, everyone should agree

that the appropriately trained person perceives that what the children are doing

is wrong—assuming that what the children are doing is wrong. So the view that

we come to know the moral facts by perception does not appear to rule out that

we come to know them by inference to the best explanation, or by inference

from constituting non-moral facts, or by inferring moral facts from a priori

moral principles together with particular moral facts. If the perceptual view is to

provide us with a distinctive answer, we need a well-motivated restriction on

what it is to know something by perception according to which the three views

we considered in the previous sections would not count as perceptual views.

Again, for all that has been said so far, a proponent of any of the views we

have discussed is free to agree with the plausible view that the appropriately

trained person can make the spontaneous knowledgeable judgment that, say,

what the children are doing is wrong, just as the wine connoisseur can make the

spontaneous knowledgeable judgment that the wine has hints of oak and berries.

So what more could be meant by saying that we perceive the moral facts? What

is needed is some way of marking the view that we can in some circumstances

perceive the moral facts as a distinct view of moral epistemology.

5.3 A digression on intuitionism, and a solution to the problem

Let us approach the problem of making the perceptual view distinctive by

way of a brief digression on Audi’s (1996) defense of intuitionism, a view that is

in some respects similar to the perceptual view. Intuitionism is standardly taken

to be the view that we get moral knowledge by a special faculty of moral

intuition. But Audi argues that intuitionism need not posit a faculty of moral

intuition ‘‘distinct from our general rational capacity as manifested in grasping

logical and (pure) mathematical truths’’ (p. 109).

Now an immediate difficulty for this view is that mathematical axioms and

logical truths are knowable a priori, and obviously we do not know particular

moral facts—that the children acted wrongly, say—a priori. Audi explicitly

222 / Sarah McGrath

recognizes this: he says that even if one were to concede that we can know a

priori generalizations such as: ‘‘If one sees someone fall off a bicycle and can

easily help with what appears to be a broken arm, one has a prima facie

obligation to do so’’, we cannot know particular moral facts a priori:

Consider…the unconditional proposition that I actually have this obligation;

this presupposes both my existence and that of the injured person(s) and hence

is plainly neither a priori nor a necessary truth. (p. 109)

But Audi’s view seems to be that the fact that mathematical axioms and logical

truths are knowable a priori, whereas moral facts about particular cases are not,

is irrelevant to the claim that we know both in virtue of our general rational

capacity. What is distinctive of intuitions, he tells us, is that they have the

following four features: intuitions (a) ‘‘must be non-inferential, in the sense

that the proposition in question is not—at the time it is intuitively held—held

on the basis of a premise; (b) ‘‘must be…moderately firm cognition[s]…one must

come down on the matter at hand’’; (c) ‘‘must be formed in the light of an

adequate understanding of their propositional objects’’; and (d) must be ‘‘pre-

theoretical: roughly…neither evidentially dependent on theories nor themselves

theoretical hypotheses’’ (pp. 109–110).

Now it is not clear that Audi, with these conditions, has explained a

distinctive and compelling version of intuitionism. (b) and (c) seem to be

features of beliefs generally, or at any rate are not distinctive features of

moral, mathematical, or logical beliefs. And since so many of our beliefs are

in some sense pre-theoretical, it is hard to see what work (d) is doing. But more

importantly, it is not clear that the basic Kantian thought—that one could know

moral facts by exercise of one’s general rational capacity—is correct: being good

at reasoning and in possession of the requisite concepts seems insufficient for

being in a position to gain moral knowledge, in the way that, arguably, being

good at reasoning and in possession of the requisite concepts is sufficient

for being in a position to gain knowledge of logical or mathematical truths.

Offhand, it seems that someone who is both good at reasoning—both theoret-

ical and practical—and armed with the requisite concepts might be blind to

morality.

However, we can extract a useful idea from Audi’s discussion. The first

feature Audi lists as distinctive of intuitions—that they are non-inferentially

justified—seems a plausible candidate for marking off the perceptual view

from the other views of moral knowledge we have discussed. On the other

views, moral beliefs are justified by distinct non-moral evidence. A distinc-

tive view that we sometimes get moral knowledge by ‘‘moral perception’’ is

this:

PA1+: We have some moral knowledge by perceiving moral facts, and this

perceptual knowledge does not rest on non-moral evidence.


Compare the case of non-moral perceptual beliefs: in particular, my belief that

there is red apple before me. What is my evidence for the claim that there is a red

apple before me? Arguably, I know this on the basis of perception without any

distinct evidence—there is no fact distinct from the fact that there is a red apple

before me on the basis of which I come to believe that there is a red apple before

me. Alternatively, perhaps I do get my belief that there is a red apple before me

on the basis of distinct evidence: my evidence is that there is a red roundish thing

before me. But then, plausibly, I know that there is a red roundish thing before

me on the basis of perception without distinct evidence.

So the distinctive thing about the revised moral perception view is not that

it holds that we can know moral facts, if at all, by perception; rather, what’s

distinctive about the view is that it holds that we can know moral facts without

having (distinct) evidence for them.

5.4 Supportive example

Here is a summary of the case for PA1þ. Assume we have moral knowledge.

If all our moral knowledge rests on distinct non-moral evidence, then either we

get moral knowledge by an inference to the best explanation of our (non-moral)

observations, or we get moral knowledge by deduction from a priori principles

plus non-moral particular facts, or some combination of the two. But these two

sources cannot account for all our (a posteriori) moral knowledge. So some of

our moral knowledge does not rest on distinct non-moral evidence. And, since

PA1 is (uncontroversially) true, PA1+ follows.

The remainder of this section provides an illustrative example, and con-

strasts it with the example of Jim and the cat. Supposing that Jim knows that

what the children are doing is wrong, this knowledge rests on his non-moral

evidence—that the children are causing pain for fun—together with his know-

ledge that it is wrong to cause pain for fun (Harman seems to think of CAT

along these lines). But this example is not entirely typical: other cases aren’t like

that. Sometimes we don’t come to know that a person acted wrongly because we

know that the person’s act has non-moral feature F, which we put together with

our previous knowledge that acts with non-moral feature F are wrong. Rather,

we don’t know any such principle, and yet we know that the person did the

wrong thing (perhaps we later revise our principles on the basis of the particular

judgment).

Here is an example of the type I have in mind: suppose Alice believes that

homosexuality is wrong, and that she believes this because she has learned that

the scriptures say that homosexuality is wrong, and believes that the scriptures

are authoritative on this matter. But then she gets to know a couple, Bob and

Chuck, who live next door. She gradually comes to believe that it is not wrong

for them to be in this relationship. It isn’t that she comes to believe this because

she detects some non-moral features that she believes are sufficient for having a

morally permissible relationship—she doesn’t change her mind because she

224 / Sarah McGrath

learns that these people are monogamous, or that they prioritize each other’s

needs. According to the moral principles that Alice believes, these sorts of non-

moral facts would be insufficient for having a relationship that is morally

permissible. Alice simply comes to believe that there is nothing wrong with

this relationship, on the basis of her acquaintance with Bob and Chuck. Further

(we may assume) Alice comes to know that there is nothing wrong with this

relationship. She might then go on to revise the principle that she originally

believed: that homosexuality is wrong.

Someone might object in response to this example that they doubt whether

Alice comes to know that there is nothing wrong with this relationship: the story

gives us insufficient reason to think that Alice’s belief that Bob and Chuck do

not have an immoral relationship amounts to knowledge. For Alice, on becom-

ing fond of Bob and Chuck, may have gradually come to believe that there was

nothing wrong with their relationship, simply because she liked them. And if

that’s true, Alice does not know. The following example might help to bring out

the worry. Suppose Karen (falsely) believes that Julie is far too law-abiding ever

to break the law, and comes to believe that riding a motorcycle without a helmet

is legal in Florida by watching Julie ride off on her motorcycle without a helmet

in Florida. In fact, it is legal to ride without a helmet in Florida, but Julie would

ride without a helmet even if it weren’t. So Karen’s belief is not knowledge: she

just got lucky, because she thinks Julie would never break the law. Similarly,

Alice’s moral belief is not knowledge: she believes Bob and Chuck are not doing

anything wrong because she likes Bob and Chuck.

But the response is just that while it is of course possible to fill out the case

of Alice in such a way that her belief does not count as knowledge, it is possible

to fill out the details of the case so that it is. I am only using the example of Alice

to illustrate the kinds of case I have in mind when I say that sometimes our

knowledge of particular moral facts is by perception, and not on the basis of

distinct, non-moral evidence. Surely in at least some cases like the one that I

have described, we would grant that the subject extends her moral knowledge,

rather than merely happening upon a true belief.

6. Q2: Do we have moral knowledge?

6.1 Harman’s answer: no

In section 2, we attributed to Harman an argument for moral skepticism

analogous to Mackie’s: this argument relied on a claim about how we would get

moral knowledge if we had it. As I’ve reconstructed it, that argument that we

have no moral knowledge (cf. the color skepticism argument in section 2.2) is:

(1M) Moral hypotheses cannot be justified by an inference to the best

explanation of our moral judgments.


(2M) If we have moral knowledge, we know moral hypotheses by an

inference to the best explanation of our moral judgments.

Hence:

(3M) We have no moral knowledge. (cf. Harman 1977, p. 13)

I have argued that since HA1 is not the correct answer to Q1, (2M) is false. But

someone might reply that in fact, we can find in that first chapter a much more

powerful argument for moral skepticism. Suppose it is granted that (2M) is false

in the argument above. Still, if we have moral knowledge, moral facts must at

least sometimes explain our moral judgments. So there is a more straightforward

argument for moral skepticism:

(1M*) Moral hypotheses do not explain moral judgments.

(2M*) If we have moral knowledge, then moral hypotheses explain moral

judgments.

Hence:

(3M*) We have no moral knowledge.

This argument does not rely on any claim about how we would get moral

knowledge, if we had it: it merely lays down an extremely plausible necessary

condition for our having moral knowledge.

(2M*) is far more plausible than (2M). But an argument for (1M*) has not

been provided. From Harman’s discussion we can only extract the result that if

we know some moral hypothesis, it is not by an inference to the best explanation

of judgments (or, more broadly, non-moral observations). And (1M*) does not

follow: it might be that while moral hypotheses are not explanatory enough to be

known by inference to the best explanation, they nevertheless do explain judg-

ments. To see this, consider:

MR. BODY: Mr. Body is found bludgeoned to death; Tom and Dick both

have motives, lack alibis, etc. In fact, Tom murdered Mr. Body, not Dick.

We cannot know by inference to the best explanation that Tom clubbed

Mr. Body—that hypothesis is not explanatory enough. Yet Tom’s clubbing

Mr. Body does explain his death.

The point is just that p might explain q, even though p is not explanatory

enough to be known by inference to the best explanation. So while everyone

should agree that if we have moral knowledge, then moral facts explain our

moral judgments, this does not force us to accept the picture of moral episte-

mology according to which our moral knowledge is justified by inference to the

226 / Sarah McGrath

best explanation. Returning to CAT, some take it that Harman has in fact

shown that moral hypotheses do not explain our moral judgments, because he

has shown that we can give a perfectly good explanation of our moral judgments

without mentioning any moral facts. But as Harman has in effect conceded in

his discussion of the color case, the fact that I can explain your judging p

without explicitly mentioning p is insufficient to show that p does not explain

your judgment.

6.2 Concluding Remarks

I have argued that if we have moral knowledge, we have at least some of it

by perception. If Jim knows that the children acted wrongly in setting the cat on

fire, then (we can suppose) he has this piece of knowledge because he perceives

that the children acted wrongly in setting the cat on fire. The crucial feature that

distinguishes the perceptual account from the others we have considered is that

Jim does not know that the children acted wrongly in setting the cat on fire on

the basis of any (distinct) evidence. He simply sees that they did, as he might

simply see that the cat is black.

Suppose that’s right: if we have any moral knowledge, we have some of it by

perception. Well, do we have any moral knowledge? In closing, I’ll make three

remarks, rather than face Q2 head-on.

First, if PA1+ is the correct answer to Q1, the question of whether we have

moral knowledge is an instance of the problem of explaining which cases of

perceptual belief count as knowledge. Second, since I have argued that we don’t

have any (distinct) evidence for some of our moral beliefs, we can straightaway

conclude that we can’t entirely answer the moral skeptic on her own terms: some

of our moral opinions cannot be justified on the basis of non-moral evidence.

But it is not clear why this result should threaten our moral knowledge. We can’t

badger the skeptic into morality—why isn’t that an interesting result, rather

than a cause for alarm? Third, this is not an abrogation of philosophical

responsibility: we can take as a starting point that torture is wrong and that

we know it is. We don’t have to agree that we must start with psychological facts

and try to argue from them to moral conclusions. The project of finding secure

foundations for knowledge in our mental states (judgments, seemings, sensa-

tions, feelings, etc.) is in general highly suspect, and should be equally dubious in

the case of morality.

Now of course there are arguments against the existence of moral facts, and

so moral knowledge. Perhaps we should conclude that there are no moral facts

because the alleged moral facts would have to exert a non-natural magnetic pull

over those who knew them. Perhaps we have no moral knowledge because there

is intractable moral disagreement. But if we set these sorts of arguments to one

side, the question of whether we have moral knowledge is not very hard to

answer. Torturing cats for fun is wrong, and—these days, at least—this fact is

widely known.


Notes

1. I am grateful to the audiences at Auburn University, Cornell University, Tufts

University, Western Washington University, and at the 2004 Inland Northwest

Philosophy Conference for helpful discussion and criticism. Thanks also to

Selim Berker, Alex Byrne, Caspar Hare, Ned Hall, Elizabeth Harman, and

Brian Weatherson.

2. While Harman appears to argue for moral skepticism in that first chapter, this is

probably not his considered view; later in the book he seems to take it that we do

have moral knowledge.

3. We can also extract from that chapter an argument for moral skepticism

that does not rely on any particular view about how we would get moral

knowledge. I will return to that in section 6 below. What concerns us here is

the idea if we had moral knowledge, we would get it in the same way that we get

scientific knowledge: by inference to the best explanation.

4. The ‘‘explanations that we will in practice give’’ are explanations of our color

experiences (see p. 22).

5. See for example Sturgeon (1988).

6. An alternative candidate for what moral hypotheses might explain is moral

seemings, for example that it seems to Jim that what the kids are doing

is wrong. A moral seeming is, plausibly, just a disposition or propensity to

make a moral judgment. But this suggestion—that we know moral hypo-

theses by inference to the best explanation of our dispositions to make moral

judgments—is no more plausible than the official suggestion that we know

moral hypotheses by inference to the best explanation of moral judgments

themselves.

7. For a helpful discussion of Hume’s arguments see Watkins (2002).

References

Anscombe, E. 1971. Causality and determination. Reprinted in Agency and Responsibility,

ed. L. Ekstrom. Boulder: Westview Press.

Audi, R. 1996. Intuitionism, pluralism, and the foundations of ethics. In Moral Knowledge?,

ed. W. Sinnot-Armstrong and M. Timmons, Oxford: Oxford University Press.

Harman, G. 1977. The Nature of Morality. Oxford: Oxford University Press.

Harman, G., and J. J. Thomson. 1996. Moral Relativism and Moral Objectivity. Oxford:

Blackwell.

Hume, D. 1980. A Treatise of Human Nature. Ed. L.A. Selby-Bigge, Oxford: Oxford University

Press.

Mackie, J. L. 1977. Ethics. Harmondsworth: Penguin.

McGinn, C. 1997. Ethics, Evil, and Fiction. Oxford: Oxford University Press.

Moore, G. E. 1903. Principia Ethica. Cambridge: Cambridge University Press.

Sturgeon, N. 1988. Moral explanations. In Essays on Moral Realism, ed. G. Sayre-McCord,

Ithaca: Cornell University Press.

Watkins, M. 2003. Cognitive complexity and epistemic simplicity: a reply to Hume.

Manuscript.

Watkins, M., and Jolley, K. 2002. Pollyanna Realism: Moral perception and moral properties.

Austrlasian Journal of Philosophy, 80: pp. 75–85.

228 / Sarah McGrath

Documents

Moral Knowledge by Perception