How We Ought to Think of “Ought” page 1
How We Ought to Think of “Ought”
I Introduction
The present essay offers a unified account of the modals
“ought,” “must,” and “is obliged to.” It argues that there are no
special moral senses of “ought” and “must.” The same predicate
may be normative in application to agents, but non-normative in
application to non-agents.1 The central theses are: 1) that
“ought” and “must” are each single, univocal modal predicates
with very wide application; 2) that “ought” is a different modal
predicate with different truth-conditions from the truth-
conditions of “must” and “is obligated to.”
This account is relevant to debates in at least two areas of
philosophy: In ethics, because much of the time what we ought to
do we are also obligated to do, and most of the time, for some
kinds of obligations, we ought to do what we are obligated to do,
“must” and “ought” are easily confused. In virtue epistemology,
there is a long-standing debate about how it can be that we ought
to believe things.2
1 Matthew Chrisman (2012), On the Meaning of “Ought” Studies in
Metaethics, vol.7
has excellent arguments for such a unification of the various
“senses” of “ought.” 2 See Chrisman, Matthew. (2008). Ought to Do. THIS JOURNAL vol
CV, 346-370.
How We Ought to Think of “Ought” page 2
Section II presents some semantic and logical facts about
“ought,” “must” and “is obligated to.” Sections III offers
theories of the truth-conditions of these modals which fit the
data in Section II. Section IV very briefly sketches some
consequences of this account for ethical theory.
My apparatus differs from that employed by most
theoreticians of modalities. Modals are not quantifications over
possible worlds but rather relations between propositions and
sets of propositions. The semantics of modals says what those
predicates are and how many places they have. The theory of
modals is an account of what has to obtain for a particular modal
predicate to be true of a proposition relative to a set of
propositions.
The treatment of modals as predicates simplifies in at least
four ways:
First, it assimilates the treatment of adverbial
modification of modals to ordinary adverbs. “Physically” in
“physically necessary” is the same predicate as it is in
“physically ugly.”
Second, it makes it relatively easy to give accounts of
complex modal expressions. “Ought very much to” fits with one’s
account of comparative adjectives if “ought” is a predicate.
“Slightly more probable than” likewise is not a special case if
“probable” is an adjective.
Third, some modals are clearly relations of a proposition to
a set of propositions. “One must register motor vehicles”
How We Ought to Think of “Ought” page 3
obviously relates “One registers motor vehicles” to a body of
laws. An account of all modals as relations between propositions
and sets of propositions thus treats modals uniformly.
For the modals that this essay discusses, “ought” “must”
“is obligated to” and “reasonably expected that,” it is simpler
just to describe the relationship a given modal predicate
expresses rather than to construct the appropriate condition on a
set of possible worlds. While heuristic models in terms of
possible worlds may illuminate some aspects of our understanding
of some modals, such heuristics do not seem to be relevant to our
understanding of all modals. For modals such as “somewhat more
likely than” and “only barely possible” the heuristic value of
thinking of the modals as quantifications over possible worlds is
obscure.
“Necessary” and “possibly” are special limit cases analogous
to the quantifiers “all” and “some.” Because “all” and “some” are
extreme quantifiers, unlike “ few” and “most,” it is possible to
represent “All frogs are green” and “Some frogs are green” as
operators on truth-functions. But provably “Most frogs are green”
cannot be so represented.3 Just as logicians were misled by
special features of the limit quantifiers “all” and “some” to
3 See Jon Barwise and Robin Cooper (1981).Generalized Quantifiers
and Natural Language. Linguistics and Philosophy 4. 159-219, citing
Nicholas Rescher (1964). Plurality Quantification. The Journal of
Symbolic Logic, vol. 27. 373-74..
How We Ought to Think of “Ought” page 4
take them to be operators,4 so contemporary linguistic theorists
are misled by the success of possible world explications of the
extreme limit modalities “is necessary” and “is possible” to
suppose that modals are quantifications over possible worlds.
Just as quantifiers are really predicates of sets, so modals are
really relations between propositions and sets of propositions.
II Some features of “ought” “must” and “obligated”
a) Non-agent subjects of “ought” and “must”
Some “ought”-sentences have nothing to do with actions by
agents. For instance, the asparagus ought to be up by now, since
it is mid-May. Asparagus has no obligations. So, at least in
these non-agent applications, “ought” means something different
from “is obligated to.” Some of these non-agent applications of
“ought” make perfect sense, but a different sense, with “must”
substituted for “ought.”
These non-agent applications of “ought” and related words5
are unlikely to be metaphorical or to be homonyms of modals that
only apply to agents. The hypothesis that we have families of
homonyms should be a last resort, rather than what we immediately
accept as the right theory.6
4 Heim, Irene and Kratzer, Angelika (1998). Semantics in Generative
Grammar. (Oxford: Blackwell Publishing) page 191.
5 There is more to say about “should,” which, besides being
virtually synonymous with “ought to,” is related to “would” and
“could,” with their relatives “will” and “can.”
How We Ought to Think of “Ought” page 5
In the next section, I propose a way to treat “ought” as
univocal throughout its applications to agents and to non-agents
and propose a similar account of “must.” “What goes up must come
down,” “You must move your king when it is in check,” and “You
must not lie” are the same “must.”
b) Obligations, requirements, and “ought”
“If you major in Philosophy, you ought to take Philosophy
2211” implies that the course is recommended but not required. On
the other hand, “If you major in philosophy you must take
Philosophy 2211” describes a requirement. My accountant’s advice,
“If you make over $100,000 per year you ought to invest part of
your income in an IRA” is quite different from “If you make over
$100,000 per year you are obligated to fill out the long form.”
Conditional “ought”-sentences do not warrant some of the
inferences warranted by conditional obligation sentences. The
guidelines may say both “A student who majors in philosophy ought
to take Philosophy 2211” and “A student who has taken Math 1101
ought not to take Philosophy 2211.” But a student who majors in
philosophy and has taken Math 1101 is not someone who both ought
and ought not to not take Philosophy 2211.
Conditional obligation sentences are obligations that a
conditional be true and true antecedents yield categorical
obligations. Thus the “must” analogs of the above “ought”-
sentences, “A student who majors in philosophy must take
6 Matthew Chrisman (2012), On the Meaning of “Ought”. Studies in
Metaethics, vol.7, makes this point.
How We Ought to Think of “Ought” page 6
Philosophy 2211,” and “A student who has taken Math 1101 must
not take Philosophy 2211,” forbid someone who has taken Math 1101
from majoring in philosophy.
As Davidson7 observes, “ought”-sentences behave in much the
way that conditional probability sentences do. Briefly,
conditional probabilities with true antecedents do not yield
categorical probabilities. The truths “Anyone against gay
marriage is probably a Republican” and “Anyone who voted for
Obama is probably not a Republican” do not jointly warrant the
conclusion that Fred, who is against gay marriage and who voted
for Obama, is probably both a Republican and not a Republican.8
Many modals have the same non-detachability feature. In
particular, from “if A it is reasonable to believe that B,” and
“A” it does not follow that it is reasonable to believe that B.
To see this, replace “probably” with “reasonable to believe that”
iin the example above. “If A it is not surprising that B” has the
same feature. I argue below that the reason these modal
conditionals do not detach is that they are relations between
propositions and sets of propositions. The “if”-clause adds an
element to the set. The consequent is then second argument in a
relation to that enlarged set.
7 Davidson, Donald. (1970). How is Weakness of the Will Possible.In Davidson (1980). Essays on Actions and Events. (Oxford UniversityPress) 21-42.
8 Hempel, Carl. (1960). Inductive Inconsistencies. Synthese Volume 12 Number 4. 439-469 makes this point..
How We Ought to Think of “Ought” page 7
The “ought” in a conditional “ought”-sentence likewise
characterizes some kind of bearing the antecedent has in relation
to the consequent,9 relative to some considerations. If “ought”-
sentences also have form analogous to modals like conditional
probability, the “antecedents” of conditional “ought” sentences
describe the bearing of the consideration in the antecedent on
the consequent. I discuss that bearing below.
c) Anankastic “ought” and “obligation” sentences
Conditional “ought”-sentences with an agent’s desire
described in the antecedent make recommendations, whereas such
conditional “must”-sentences state requirements. “If you want a
hamburger, you ought to try Joe’s Grill” makes a recommendation
which is not a requirement. On the other hand, “If you want a Big
Mac, you must go to MacDonald’s” describes what is required in
order to satisfy your desire.
9 In modals other than the extreme ones, “antecedent” and
“consequent” are misleading. David Lewis proved that conditional
probability cannot be the categorical probability of any
conditional. (Lewis, David. (1976) Probabilities of Conditionals
and Conditional Probabilities. Philosophical Review 85 (3). 297-
315.) “If” marks the conjectural addition to the modality base.
How We Ought to Think of “Ought” page 8
As several have noted,10 the anankastic conditionals with
“ought” have multiple understandings. Both “If you want heroin,
you ought to contact Fred” and “If you want heroin, you ought to
enter a drug rehabilitation program” can be understood as truths.
The possibility of multiple readings suggests that “ought”-
sentences are relative to sets of considerations.
c) Peculiarities of “must”
“Must,” although often inter-changeable with “is obliged to”
applies much more widely. It applies to non-agents, as in “What
goes up must come down.” “Must,” although akin to “is necessary”
is actually sometimes weaker than “is.” “Must” implies an
inference from something. When I say “This must be Spring
Street,” relying on the guy at the gas station, “This is Spring
Street” would convey more confidence.
d) Prima facie obligations
Many ethicists explain some of the differences between
“ought” and “obligation” by the concept of “prima facie
obligation,”11 that many “ought”-principles are ceteris paribus
principles, but still principle of obligation. This idea is
10 For instance, Von Fintel, Kai and Iatridou, Sabine,(2008). How
to Say Ought in Foreign: The Composition of Weak Necessity
Modals, in Gueron and Lecarme, (ed.s) Time and Modality. (Springer),
115-41.11 Ross, W. D. (1930). The Right and the Good. (Oxford University
Press.)
How We Ought to Think of “Ought” page 9
inadequate. First, it applies only to “ought”s which involve
agency. Defeasible weather-principles need some other account.
Second, the resemblance of “ought”-sentences to conditional
probability sentences argued for by Davidson12 suggests that the
relationship between the antecedents of conditional “ought”
sentences and their consequents is unlike that between
antecedents and consequents of “must” and “is obligated to”
sentences. Third, there is no plausible way to treat normal
anankastic “ought”-sentences as obligations of any sort.
The next section replaces “prima facie obligation” with an
account that respects the linguistic and logical differences
between “ought” and “is obligated.” .
III Theories of “ought,” “must,” and “is obligated”
a) Preliminary: Consideration-bases
A consideration-base13 for a modality is a set of
propositions. “Ought”, “must,” and “is obligated to” are two-
place relations between such bases and the proposition in the
content clause. What consideration-base a speaker means is guided
12 Davidson, Donald. (1970). How Is Weakness of the Will
Possible?. In Davidson (1980). Essays on Actions and Events. (Oxford
University Press) 21-42.
13 I use “consideration-base” rather than “modal base” because
the concept is somewhat different from that used by Angelika
Kratzer (2012) Modals and Conditionals. (Oxford University Press)
and others. Consideration-bases are sets of propositions.
How We Ought to Think of “Ought” page 10
by, but not determined by, context. “Ought” and “must” both have
consideration-bases, but these bases have different requirements.
These modals also express different relations between the base
and the content clause.
Consideration-bases can be referred to without being listed
and without the speaker having a criterion for whether a given
proposition is in the set. So, “Fred’s self-interest,”
“Connecticut statutes,” “how things are,” and “the laws of
nature” all refer to sets of propositions. This is obvious with
consideration-bases associated for “must” that are
uncontroversially sets of propositions. For “You must not turn
left at red lights” the usual consideration-base is traffic laws.
But few can quote the relevant statute.
Consideration-bases for true “ought” sentences are sets of
truths--the data relative to which the proposition following
“ought” is evaluated. There are different consideration-bases for
a given “ought”-sentence, and different truth-values relative to
those different consideration-bases. The relation between a
consideration-base and the proposition following “ought” is
“idealized reasonable expectation,” explicated below. Conditional
“ought” sentences add the proposition in the antecedent to the
consideration-base and evaluate the support that that enlarged
base would give to the proposition following the “ought.”
Consideration-bases for “must” and “is obligated” sentences
are also sets of propositions, but they need not be truths.
Distinct consideration-bases can be law codes, rules of chess,
How We Ought to Think of “Ought” page 11
information from tour schedules, and laws of nature, along with
information about particular circumstances. While these
consideration-bases may be expressed as imperatives, their
content, is a proposition with a truth-value. So, “Thou shalt not
kill,” as a component of a consideration-base, is a false
universal description of the behavior of those to whom it
applies. None of them kill. The relation between a given
consideration-base and the “must” sentence is “consequence.”
Conditional “must” sentences thus can be treated indifferently
either as conditionals that are consequences of the
consideration-base, or as adding the antecedent of the
conditional to the consideration-base. That is, when “if A then
you must make it the case that B” is true, then so is “You must
make it the case that if A then B.”
There are several possible consideration-bases for any given
“must” or “ought” sentence. We interpret a modal utterance by
assigning some consideration-base. That assignment is guided, but
not infallibly, by context and plausibility. The speaker’s
intention fixes the consideration-base.
Unusual and unlikely bases may be intended, just as
improbable readings may be correct. One of the syntactically
possible readings of “My dog stays at a clean, expensive pet
kennel” implies that this kennel is for clean, expensive dogs.
Since such kennels are unlikely, we are unlikely to assign that
reading. But a speaker could mean that. An utterance of “You must
not kill people” likewise has several possible consideration-
How We Ought to Think of “Ought” page 12
bases. Struck by Hagar’s tender demeanor, I remark to him “You
must not kill people.” A speaker can intend a base whether or not
context makes it salient. A speaker who wants to communicate may
use an adverb such as “logically,” “morally,” or “for his own
sake” to make the intended consideration-base clear.
The requirement for being possibly understood means that not
just any set of propositions can be a consideration-base. Given
that language use is primarily communication, only a
consideration-base that another can grasp is a possible
consideration-base.
b) “Ought”
If the same modal applies to non-agents and agents,
something about non-agent attributions also applies to agent
attributions. The obvious feature of non-agent “ought” is that,
relative to the consideration-base, the content clause is also to
be reasonably expected, another modal. What the weather ought to
be tomorrow and how far the flood waters ought to have progressed
are equally well described as what can be reasonably expected,
given the consideration-base, the relevant facts.
For this relation to provide the link between non-agent
“ought” and “ought”s that apply to agents, the modals “ought” and
“reasonably expected” have to be connected and there must be
reasonable expectations of an appropriate kind about agents. I
propose that “ought” holds between a consideration-base and a
proposition just in case there is a chain of reasonable
expectations from the considerations in the base to the
How We Ought to Think of “Ought” page 13
proposition. I propose further that interpreting entities as
rational agents is applying reasonable-expectations principles
from consideration-bases that take into account interpretive
principles about agents.
b1) “ought” as a chain of reasonable connections relative to a
consideration-base
For the first part of the link, I explicate “ought” as an
idealization of “reasonably expected relative to a consideration-
base.” By an idealization, I mean a chain of conditional
reasonably expected propositions, relative to a consideration-
base, such that the consequent of the element n is the antecedent
of element n+1. For example, relative to a consideration-base
consisting of truths about the sums and products of one-digit
numbers an agent, as a believer in truths, can reasonably be
expected to get the right answer to any such multiplication. With
that consideration-base, there is a chain of reasonable
expectations such that the result of multiplying two seven-digit
numbers ought to be the arithmetically correct result. So,
relative to just the truths of arithmetic, and the reasonable
expectation that an agent will get simple calculations right, the
agent ought to get the arithmetically correct result.
However, we cannot reasonably expect a human calculator to
get the mathematically right result, for a very long calculation.
Rather, relative to a consideration-base that abstracts from
human imperfection, there is a chain of reasonable expectations
to the mathematically right result.
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If the consideration-base includes the further information
that the agent is a fourth grader new to multiplication, we can
still reasonably expect him to get the right answer only most of
the time when multiplying or adding one-digit numbers. After many
such calculations, it will be true that he ought to have made a
mistake by now. So, the number he ought to have come up with
ought to be different from the correct mathematical answer. Since
he is both an agent and a fourth-grader, both “ought”-sentences
are true, relative to different consideration-bases.
An idealization of “can be reasonably expected to,” relative
to a consideration-base, is what would result from a sequence of
events if what could reasonably be expected to happen at each
stage in the sequence, relative to the consideration-base,
happened at every stage. If the chain is very short, as with “If
you turn the key, the car ought to start,” “ought” and
“reasonably expected that” can amount to the same thing relative
to a base.
The difference between “ought” and reasonable expectation
relative to a consideration-base is that an idealization can
involve very long chains of steps. Since a reasonable expectation
that p and a reasonable expectation that q if p need not imply a
reasonable expectation of q, chains of reasonable expectations
result in diminished reasonable expectation. Many modals have the
same feature, such as “it is not surprising that” and “probably.”
The result of the diminution is that we cannot reasonably expect
an agent to get the correct mathematical result in a long
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calculation, even relative to a consideration-base that the agent
is an agent, and so inferring truths, and the truths of
arithmetic. What ought to be may differ from what is reasonably
to be expected.
Since “ought” draws consequences for the consequent relative
to a consideration-base, a base can take special circumstances
into account. Thus, lottery paradox problems do not arise. Our
reasonable expectation, of each lottery ticket, that it will not
win will not lead to the conclusion that it ought to be that no
ticket wins, because the proposition that someone wins is part of
an appropriate consideration-base. The chain would in effect
build up a conjunction of claims that individuals will not win.
The fact that it is a lottery blocks the “ought”-claim that
everyone in the conjunction fails to win. One of these tickets
ought to have won. That is, each of the reasonable expectations
is a reasonable expectation relative to the consideration-base.
In this special circumstance, the consideration-base includes the
fact that these are tickets in a lottery. So, even though of each
individual, we can say both that it is reasonable to expect it to
lose and that it ought to lose, we do not get the result that
they ought to all lose.
This is parallel to the chain of reasonable expectations in
the case of the fourth grader. Just as it begins to be true that
he ought to have made a mistake by now, so it begins to be true
that one of the people we have considered ought to have won. The
lottery imposes an addition to the consideration-base that
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requires that the fact that it is a lottery be part of the
consideration-base at every step, and eventually becomes relevant
to whether an “ought”-sentence is true.
b2) reasonable expectations of agents as rationality
Just in virtue of an entity’s being an agent, we can
reasonably expect that entity to be aware of objects in its
environment, to reason as we do, and want things we want. These
elementary reasonable expectations of agents are, for instance,
part of Davidson’s account of interpretation. In Davidson’s 14
phrase, we interpret agents’ behavior by making them maximally
“believers of the true and seekers of the good.”
Maximization principles of interpretation are thus
reasonable expectations with the consideration base including “is
an agent.” Some applications of these principles are more
reasonably expected than others. Basic beliefs, such as that
there are physical objects, and basic desires, such as dislike of
intense pain, are ascribed to agents with great warrant. Other
desires and beliefs, such as a desire to play contract bridge or
the belief that Augusta is the captal of Maine, are not so
central. A consideration-base including differences in perceptual
history explains why some of our beliefs are not shared by
another agent. But, relative just to the consideration-base that
14 On page 222 of Donald Davidson, (1970). Mental Events. In
Davidson (1980). Essays on Actions and Events. Oxford University Press.
207-227.
How We Ought to Think of “Ought” page 17
the other is an agent, what we believe and want is reasonable to
assign to the other agent. Thus, even though we do not expect
another agent to know what we know, there is a consideration-base
restricted to just the agency of the other, what we take to be
the truths, and our beliefs and desires, from which a chain of
reasonable expectations follows. “She ought to flee, because
the flood waters are coming,” can be true even though she has no
way of knowing about the flood. That consideration-base rests on
the reasonable expectation, relative just to being an agent, she
believes what we believe about the flood waters. Relative to
another base including her epistemic position relative to flood
information, she ought to stay at her desk.
What Fred ought to do may be relative to a consideration-
base which includes preferences peculiar to Fred. The “ought”-
sentence with that base may differ from what Fred morally or
prudentially ought to do. “Fred ought to be very drunk by now.”
On the other hand, the consideration-base which leaves out Fred’s
self-interest, odd preferences, and weaknesses and just includes
what Fred can be expected to want just given that he is a
rational agent, provides starting points for a chain whose last
element is a candidate for what Fred morally ought to do.
The notion of rationality constrains contents of desires as
well as the structure of practical inference. Interpretation of
action is only possible given such content constraints. If all
desires were equally rational, then any behavior would have an
optimal interpretation as an intentional action that reflected
How We Ought to Think of “Ought” page 18
perfectly correct beliefs. For instance, if a person drops a
large rock on her foot, the interpretation that she wanted pain
and knew that rocks landing on feet produce pain would be as
acceptable as supposing the event to be accidental. Irrational,
otherwise not-reasonably ascribed desires can be attributed to a
rational agent, but only on the basis of having ascribed other
desires we share and so can understand.
b3) “ought” and consideration-bases
Even in the simple non-agent attributions of “ought” the
same “ought”-sentence may have different truth-values with
different consideration-bases. From a consideration-base
consisting of general truths about small gasoline engines it is
unreasonable to expect that my mower will start will one pull of
the starting cord. However, given that it is a Honda, that is,
adding “This is a Honda” to the consideration-base, it should
start with one pull.
Conditional probability was proven by Lewis15 not to be a
probability applying to a conditional. I am supposing that
“reasonably expected” is a modal like conditional probability in
this respect. Thus, an idealization of “if p, it can be
reasonably expected that q,” that is, “if p, then ought q,” is
not an “ought” applied to a conditional. The bearing of the
15 Lewis, David. (1976). Probabilities of Conditionals and
Conditional Probabilities. Philosophical Review 85 (3). 297-315.
How We Ought to Think of “Ought” page 19
consideration-base on an “ought”-sentence is an idealization of
reasonable expectation.
The “antecedent” of a conditional “ought”-sentence
supplements the consideration-base with another proposition, and
the “ought” is evaluated relative to that expanded set. So, “If
George wants a hamburger, he should go to Joe’s Grill” appraises
the idealized support “George goes to Joe’s Grill” gets relative
to a consideration-base which just includes George’s situation
with respect to hamburger vendors and interpretive maxims about
the connection between desires and action, supplemented by the
supposition that George wants a hamburger. Relative to another
consideration-base which includes George’s long-term self-
interest, his heart condition and the effects of saturated fat,
“If George wants a hamburger, he ought to have something
healthier” might be true.
The links of a chain of reasonable expectations making a
prudential “ought” true are reasonable expectations about what an
agent can reasonably be expected to believe and want. The
prudential “ought” is thus an idealization of someone with good
information and reasonable desires. An anankastic “ought” has an
antecedent adding a particular desire, and the consequent is an
action optimal for a person with reasonable desires, correct
beliefs, and the desire mentioned in the antecedent. Different
bases yield different true anankastic “ought”’s. Someone wanting
heroin ought to see Fred the dealer or get into rehab, depending
on the base.
How We Ought to Think of “Ought” page 20
“Ought”-sentences about an agent’s action thus can be
several ways ambiguous, depending on the intended consideration-
base. Suppose Sue is playing chess with Nero, it’s her move, and
there is a mate in two starting with a bishop sacrifice on f7:
First, if the consideration-base is just chess goals, then
Sue ought to go bishop to f7 check.
Second, relative to a consideration-base that includes Sue’s
welfare, bishop to f7 check is not what she ought to do. Nero may
take losing very badly.
Third, Nero would be a better emperor if he learned
humility, and losing quickly to Sue may bring this about. The
improvement of life in the Empire that would result from having a
humbler emperor, for Sue and everyone else, makes bishop to f7
check worth the risk. This last consideration-base abstracts from
Sue’s partiality to herself and qualifies as a moral “ought.”
Many other bases may apply. “Sue ought to be under
considerable stress at this point” one observer says truly to
another, intending a consideration-base including information
about how people in such dangerous situations feel.
To summarize: There are different kinds of bases for
reasonable expectations, and so for the “ought”s that are their
idealizations. In the above case, the aims of chess, the over-all
aims of self-preserving humans, the interests of humans
generally, and special expectations about particular individuals
yield various truth-values for the same “ought”-sentence. Given
How We Ought to Think of “Ought” page 21
the position on the board, whether Sue ought to go bishop f7
check depends on what consideration-base is intended.
One could object that this account of “ought” is not
“oughty.” By this account, “ought”s derive from our reasonable
expectations about what a rational agent can be expected to do.
Why should this motivate the agent herself?
First, only “ought”s based on consideration-bases including
what it is to be a rational agent motivate. “Ought”s based on
other than rational-agent consideration-bases do not motivate.
Fred has no motivation to be uncomfortable during the interview
just because he ought to be, given his shyness.
Second, “ought”s resting on consideration-bases that include
expectations about intentional behavior and intentional states
should motivate. Since an agent has to conceive of herself as an
agent, the fact that any agent in these circumstances can
reasonably be expected to act in a certain way is relevant to an
agent’s decision-making. If you expect anyone in your
circumstances to do a given action, you do so by interpreting the
person, that is, by maximizing the agreement between you and the
other. So, you ascribe to the other your beliefs, inference-
patterns, and desires, other things being equal. So, to be aware
that taking an action would be reasonably expected in virtue of
being a rational agent is to be motivated. That’s you. These
expectations reflect norms.
On the Davidsonian perspective, normativity is derived from
rational agency. The content of the concept of rational agency is
How We Ought to Think of “Ought” page 22
embedded in our practices of interpreting each other’s actions,
whether speech actions or not. The maxims of interpretation are
reasonable expectations relative to considerations. If the entity
being interpreted is an agent, this reasonable expectation is
normative and is part of ascribing rationality. The Davidsonian
idea thus follows Kant—the normative is grounded in the very idea
of acting for a reason. A difference is that for a Davidsonian,
the very idea of agency is about reasonable expectations, rather
than universal principles, since the observance of a given maxim
is reasonably maximized rather than absolutely required.
c) “Must”
“Must” is a consequence relation between a proposition and a
consideration-base. If the propositions in the consideration-base
are true, “must” amounts to necessitation. If the propositions in
the consideration-base are not true, the proposition may or may
not be true.
The consideration-base for “What goes up must come down” are
“the laws of nature,” and are true. The consideration-base need
only be referred to, not enumerated. When we say “You must not
shoplift” we appeal to a modal base, the laws of our region, but
very few of us can state even one of those laws. We can say what
must be given the laws of nature without having a even a
criterion for what those laws are.
The consideration-bases of which the content-clause of a
“must” sentence is a deductive consequence have a role similar to
that of “ought”-sentences. Rules of chess, laws of nature, and
How We Ought to Think of “Ought” page 23
the like are typical consideration-bases for “must.” “Must”’s
consideration-base and its relation to that base differs from
“ought”’s base and relation to its base in two ways: First,
rather than being a matter of idealized reasonable expectation,
“must”’s content clauses are deductive consequences of the
consideration-base. Second, the elements of the consideration-
bases for true “must” sentences need not be true, while those of
true “ought”-sentences must be true. “All persons do not
understate their income” does not describe the behavior of those
who must not understate their income.
“Must”-sentences are relative to consideration-bases in much
the same way that “ought” sentences are. There are “must”s true
of Sue’s chess game with Nero. Sue must move her pieces at less
than the speed of light. Since this “must” is supported by truths
about the world, Sue will so move his pieces. Sue must move her
bishop only along a diagonal, since that is a consequence of the
rules of chess. Players usually do so move their pieces, but Sue
might decide to move her bishop as if it were a knight.
Since they are only correct if the content clause is
correct, “epistemic” “must”s have true consideration-bases,
namely the relevant facts. When the tourist says, “Since it’s
Tuesday, this must be Belgium” the “must” may be justified by the
tour schedule. The tour schedule, though, is optimistic, and the
bus is still in Holland. So, the tourist is wrong. The “must” in
these sentences says what must be, given the relevant facts. The
tour guide is the warrant from which the speaker justifiably
How We Ought to Think of “Ought” page 24
conjectures that the relevant facts, what is the case, have the
content clause as a consequence.
The “epistemic” aspect of epistemic “must”s is not a matter
of the consideration-base being propositions known. Rather,
epistemic “must”s are asserted on the basis of the speaker’s
inference from known propositions in the consideration-base to
the rest of the consideration-base. So they are weaker than the
non-modal assertion.
Since contents of “must” sentences are consequences of
consideration-bases, conditional “must”-sentences are
conditionals that are consequences of sets of propositions. A
conditional “must” sentence is indifferently a relation of a
consideration-base to a conditional or a relation of a
consideration-base, supplemented by the antecedent, to the
consequent. Therefore given that “If a taxpayer earns more than
$100,000, a long form must be submitted” and “Fred earns more
than $100,000” are both true, “Fred must submit a long form” is
also true. Conditional “must”-sentences support detachment of the
consequent given the truth of the antecedent, unlike conditional
“ought”-sentences.
IV) Moral “ought” and moral obligation
A detailed treatment of what this account of “ought,”
“must,” and “is obligated” would imply about ethics and meta-
ethics is beyond the scope of this essay. This brief last section
suggests a few consequences of this account of these modals.
a) Moral “ought”
How We Ought to Think of “Ought” page 25
Most importantly, if “ought” is the central ethical notion,
ethical reasoning is more akin to induction rather than to
deduction. This means that ethical reasoning to a conclusion C
can, with further information, become reasoning to not-C. Unlike
deduction, inductive arguments can be weakened by additional
premises.
Moral “ought”s are objective if there is a consideration-
base that yields their content. Showing that there is such a base
and discerning what its elements are is the traditional project
of ethicists. A candidate consideration-base would be those
desires that agents can be expected to have just relative to
being agents, together with true beliefs about a situation. That
candidate for the moral “ought” abstracts from partiality. Given
reasonable desires and beliefs, and the impartiality that
abstraction from self-interest requires, a person ought to desire
what is morally correct.
c2) Moral “ought”s without agents
“There ought to be world peace” and other such apparently
moral “ought”s are not about particular agents. A consideration-
base whose elements have consequences about reasonable
expectations whose idealization would yield the content of such
an “ought”-sentence would include facts about agents
collectively.
“Ought to be” sentences are only true of what agents can
bring about. The existence of good fairies is not in the power of
any human agent or group of agents to bring about. Therefore,
How We Ought to Think of “Ought” page 26
“There ought to be good fairies” is false even though that would
be a good thing. We have reasonable expectations that people
generally want what is desirable. Given that a person is in a
position to act on a desire, it is reasonable to expect that the
person will do so. On Davidsonian interpretive grounds, when
something would be a good thing, people in a position to do it
ought to do it. So, for things under the power of people
collectively, or of some subset of people collectively, some of
those things ought to be the case. The moral “ought to be” is
just the moral “ought” without specificity about agency. What
ought to be is what some unspecified agents ought to do or have
done.16
c3) Moral obligation
“Is obliged to” is the special case of the modal relation
“must” which is strictly true only of agents. Obligations are
deductive consequences of consideration-bases which include
truths about circumstances. I have an obligation to report all of
my income. If I am a slave, I have an obligation to obey my
master. If I am playing chess, I have an obligation to move my
king if it is in check.
Among the consideration-bases of “obligation” sentences are
those that deal with human relations. Bases containing
16 The present theory thus agrees with Matthew Chrisman (2011)
“Ought” and Control. Australasian Journal of Philosophy. 1-19 and
Stephen Finlay and Justin Snedegar, Justin. (forthcoming) One
Ought Too Many. Philosophy and Phenomenological Research.
How We Ought to Think of “Ought” page 27
propositions such as “People do not lie” and “People keep
promises” yield obligations for which there are good reasons to
think that, by and large, they coincide with what a person ought
to do. Those reasons are reasons that appeal to rationality—why
it is that a person would, behind the veil of ignorance, choose
such restrictions, or why it is that a person cannot thoroughly
conceive of herself as a rational actor while ignoring the ends
of other agents.
Obligations deriving from such consideration-bases would
coincide with what a person ought to do, relative just to being
an agent, to the extent that there was a rational ground for
expecting that, by and large, people should not lie, should keep
promises, and so forth. The justification of the approximate
truth of such principles would be the demonstration that these
principles were rational. If that could be done, then the
principles of moral obligation would be part of the rationality
that we attribute reasonably to rational agents.
There may be chains of consequences from consideration-bases
for “must” that always conform to what a rational agent ought to
do, all things considered. For instance, Kant’s17 argument that
it is irrational to favor one’s own interests and not take into
consideration those of other agents could be something that any
rational agent ought to accept, given that the agent is a
17 Kant, Immanuel. (1785). Groundwork of the Metaphysics of Morals. In
Kant (1983) Ethical Philosophy, James Ellington, translator. Hackett.
How We Ought to Think of “Ought” page 28
rational agent, as interpretation supposes. Likewise, Nagel’s18
argument that a person motivated by her own future interests is
irrational not to take other agents’ interests as relevant to her
decisions might be sound. In that case, moral principles, in the
strict sense, would be consequences of rationality. Then a few
moral obligations would in fact be universal moral “ought”s—the
guidelines governing the interpretation of rational agents would
turn out to have these consequences. Moral principles, that
directly determine particular actions, though, such as “Do not
lie” and “Keep your promises” would be rules of thumb. Their
application would be mostly true in actual cases, and mostly true
for good reasons having to do with human interaction.
18 Nagel, Thomas. (1970). The Possibility of Altruism. Clarendon Press: Oxford.
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