WHAT ARE THE DESCRIPTIVE
You should now be able to identify value assumptions—very important hidden
components of prescriptive arguments. When you find value assumptions, you
know pretty well what a writer or speaker wants the world to be like—what
goals she thinks are most important. But you do not know what she takes for
granted about the nature of the world and the people who inhabit it. Are they
basically lazy or achievement oriented, cooperative or competitive, and rational
or whimsical? Her visible reasoning depends on these ideas, as well as
upon her values. Such unstated ideas are descriptive assumptions, and they
too are essential hidden elements of an argument.
The following brief argument about a car depends on hidden assumptions.
Can you find them?
This car will get you to your destination, whatever it may be. I have driven this
model of car on multiple occasions.
This chapter focuses on the identification of descriptive assumptions.
( j j Critical Question: What are the descriptive assumptions?
Descriptive assumptions are beliefs about the way the world is; prescriptive
or value assumptions, you remember, are beliefs about how the world
Illustrating Descriptive Assumptions
Let's examine our argument about the car to illustrate more clearly what we
mean by a descriptive assumption.
The reasoning structure is:
CONCLUSION: This particular car will get you where you want to go.
REASON: This model of car has functioned well on multiple occasions.
The reasoning thus far is incomplete. We know that, by itself, a reason just
does not have the strength to support a conclusion; the reason must be connected
to the conclusion by certain other (frequently unstated) ideas. These
ideas, if true, justify treating the reason as support for the conclusion. Thus,
whether a reason supports, or is relevant to, a conclusion depends on whether
we can locate unstated ideas that logically connect the reason to the conclusion.
When such unstated ideas are descriptive, we call them descriptive assumptions.
Let us present two such assumptions for the above argument.
ASSUMPTION 1 : From year to year a particular model of car has a consistent quality.
First, no such statement was provided in the argument itself. However, if
the reason is true and if this assumption is true, then the reason provides some
support for the conclusion. But if not all model years have the same level of
dependability (and we know they do not), then experience with a model in previous
years cannot be a reliable guide to whether one should buy the car in the
current model year. Note that this assumption is a statement about the way things
are, not about the way things should be. Thus, it is a descriptive connecting assumption.
ASSUMPTION 2: The driving that would be done with the new car is the same kind driving that was done by the person recommending the car.
When we speak about "driving" a car, the ambiguity of driving can get us into
trouble if we do not clarify the term. If the "driving" of the person recommending
the car refers to regular trips to the grocery store on a quiet suburban street with
no hills, that driving experience is not very relevant as a comparator when the new
car is to be driven in Colorado, while pulling a heavy trailer. Thus, this conclusion
is supported by the reason only if a certain definition of driving is assumed.
We can call this kind of descriptive assumption a definitional assumption
because we have taken for granted one meaning of a term that could have
more than one meaning. Thus, one important kind of descriptive assumption
to look for is a definitional assumption—the taking for granted of one meaning
looks like in argument form:
Once you have identified the connecting assumptions, you have answered
the question, "On what basis can that conclusion be drawn from that reason?"
The next natural step is to ask, "Is there any basis for accepting the assumptions?"
If not, then, for you, the reason fails to provide support for the conclusion. If so,
then the reason provides logical support for the conclusion. Thus, you can say
reasoning is sound when you have identified connecting assumptions and you
have good reason to believe those assumptions.
Attention: A descriptive assumption is an unstated belief about how the
world was, is, or will become.
When you identify assumptions, you identify ideas the communicator
needs to take for granted so that the reason is supportive of the conclusion.
Because writers and speakers frequently are not aware of their own assumptions,
their conscious beliefs may be quite different from the ideas you identify
as implicit assumptions. When you then make the hidden connecting tissue of
an argument visible, you also contribute to their understanding of their own
argument and may thereby guide them to better beliefs and decisions.
USING THIS CRITICAL QUESTION
After you have found descriptive assumptions, you want to think about
whether there is a strong basis for accepting them. It is certainly fair for you
to expect the person making the argument to provide you with some justification
for why you should accept these particular assumptions. Finally, if the
assumption is not supported and you find it questionable, you are behaving
responsibly when you decide not to buy the argument. Your point in rejectingit is not to disagree with the conclusion. Instead, you are saying that you cannot
accept the conclusion based on the reasons offered so far. In other words, you
are quite willing to believe what you are being told, but as a critical thinker you
are in the business of personal development. That development can take place
only when you accept only those conclusions that have persuasive reasons.
Clues for Locating Assumptions
Your task in finding assumptions is to reconstruct the reasoning by filling
in the missing links. You want to provide ideas that help the communicator's
reasoning "make sense." Once you have a picture of the entire argument, both
the visible and the invisible parts, you will be in a much better position to
determine its strengths and weaknesses.
How does one go about finding these important missing links? It requires
hard work, imagination, and creativity. Finding important assumptions is a difficult
You have been introduced to two types of assumptions—value assumptions
and descriptive assumptions. In the previous chapter, we gave you several
hints for finding value assumptions. Here are some clues that will make your
search for descriptive assumptions successful.
Keep thinking about the gap between the conclusion and reasons. Why are you
looking for assumptions in the first place? You are looking because you want to
be able to judge how well the reasons support the conclusions. Thus, look for
what the writer or speaker would have had to take for granted to link the reasons
and conclusion. Keep asking, "How do you get from the reason to the conclusion?"
Ask, "If the reason is true, what else must be true for the conclusion to follow?" And, to
help answer that question, you will find it very helpful to ask, "Supposing the
reason(s) were true, is there any way in which the conclusion nevertheless could be false?"
Searching for the gap will be helpful for finding both value and descriptive
Look for ideas that support reasons. Sometimes a reason is presented with no
explicit support; yet the plausibility of the reason depends on the acceptability
of ideas that have been taken for granted. These ideas are descriptive assumptions.
The following brief argument illustrates such a case:
CONCLUSION: All high-school English classes will go see at least one Shakespeare play.
REASON: It is beneficial to experience Shakespeare's works first hand.
What ideas must be taken for granted for this reason to be acceptable?
We must assume:
(a) The performance will be well done and reflective of what Shakespeare would
(b) students will understand the play and be able to relate it to Shakespeare.
Both (a) and (b) are ideas that have to be taken for granted for the reasons
to be acceptable and, thus, supportive of the conclusion.
Identify with the writer or speaker. Locating someone's assumptions is often
made easier by imagining that you were asked to defend the conclusion. If you
can, crawl into the skin of a person who would reach such a conclusion.
Discover his background. Whether the person whose conclusion you are evaluating
is a corporate executive, a labor leader, a boxing promoter, or a judge,
try to play the role of such a person and plan in your mind what he would be
thinking as he moves toward the conclusion. WTien an executive for a coal
company argues that strip mining does not significantly harm the beauty of
our natural environment, he has probably begun with a belief that strip
mining is beneficial to our nation. Thus, he may assume a definition of beauty
that would be consistent with his arguments, while other definitions of beauty
would lead to a condemnation of strip mining.
Identify with the opposition. If you are unable to locate assumptions by taking
the role of the speaker or writer, try to reverse roles. Ask yourself why anyone
might disagree with the conclusion. What type of reasoning would
prompt someone to disagree with the conclusion you are evaluating? If you
can play the role of a person who would not accept the conclusion, you can
more readily see assumptions in the explicit structure of the argument.
Recognize the potential existence of other means of attaining the advantages
referred to in the reasons. Frequently, a conclusion is supported by reasons
that indicate the various advantages of acting on the author's conclusion.
When there are many ways to reach the same advantages, one important
assumption linking the reasons to the conclusion is that the best way to attain
the advantages is through the one advocated by the communicator.
Let's try this technique with one brief example. Experts disagree about how
a person should establish financial stability. Many times young people are
encouraged to establish credit with a credit card. But aren't there many ways to
establish financial stability? Might not some of these alternatives have less serious
disadvantages than those that could result when a young person spends too much
on that credit card? For example, investing some money in a savings account
or establishing credit by maintaining a checking account are viable routes to
establishing financial stability. Thus, those who suggest that people get credit
cards to help establish financial stability are not taking into account the risks
involved with their solution or the possibility of fewer risks with an alternative.
Avoid stating incompletely established reasons as assumptions. When
you first attempt to locate assumptions you may find yourself locating a stated
reason, thinking that the reason has not been adequately established, and
asserting, "That's only an assumption. You don't know that to be the case." Or
you might simply restate the reason as the assumption. You may have correctly
identified a need on the part of the writer or speaker to better establish the
truth of her reason. While this clarification is an important insight on your part,
you have not identified an assumption in the sense that we have been using it
in these two chapters. You are simply labeling a reason "an assumption."
Here is an example of stating an incompletely established reason as an
The ratings are going through the roof for Science Fiction shows. The advertising
agencies have done a great job.
Now, challenge the argument by identifying the following assumption:
The writer is assuming that advertising is causing the ratings to rise.
Do you see that when you do this, all you are doing is stating that the
author's reason is her assumption—when what you are probably really trying to
stress is that the author's reason has not been sufficiendy established by evidence.
Applying the Clues
Let's look at an argument about the importance of planning and see whether
we can identify descriptive and value assumptions.
Planning is a valuable tool. Students need to be taught how to budget time
and write down tasks. The best way to show college students how helpful careful
planning can be for them is to require them to use a planner. Given the average
course load that students take, they will have a difficult time remembering all of
their assignments. Unlike high school, colleges do not have concerned adults
who will remind them about assignments or ask them whether they have done
their homework before they go out.
Requiring the use of a planner will help students become the goal-oriented
students that every college professor wants to have in his classroom. Such a
requirement will not only help students tremendously, but will also create a
more successful college environment for everyone involved.
CONCLUSION Planning should be a requirement for students, and the best way to accomplish
this goal is to require than to use a planner.
REASONS: 1. Students out of high school are not ready or independent enough to for
classes—planning can change that.
2. Students will become goal-oriented.
First, note that the author provides no "proof for her reasons. Thus,
you might be tempted to state, "Those reasons are only assumptions; she does
not know that." Wrong! They are not assumptions! Remember: identifying lessthan-
fully established reasons, though important, is not the same as identifying
assumptions—ideas that are taken for granted as a basic part of the
Now, let's see whether any descriptive assumptions can be found in the
argument. Remember to keep thinking about the gap between the conclusion
and the reasons as you look. First, ask yourself, "Is there any basis for believing
that the reason(s) might not be true?" Then ask, "Supposing the reason(s)
were true, is there any way in which the conclusion nevertheless could be
false?" Try to play the role of a person who does not believe a planner should
be a requirement.
Look at the two reasons. The first would be true if it were the case
that the students being described are independent learners. This author is
assuming that no such ability to take initiative for one's own academic success
exists. How can she know such a thing? Perhaps forcing students to plan would
only cause the students to have another disorderly thing to do. Thus, one
descriptive assumption is that students cannot learn to become responsible learners
Let's now suppose that the second reason is true. Planning still might
not be useful to the student. Just because the author believes in the value
of planning does not mean that it will change the lives or the study habits of
students. Thus, an assumption connecting the first reason to the conclusion is
that students will learn how to plan and then will implement that strategy later. This
assumption also links with the second reason closely.
Consider the second reason. It is true only if the student not only
absorbs the ideas of planning, but also uses them. The author is also assuming
that the ideas learned through planning will then lead to a goal-oriented lifestyle. Another important assumption is that students will change their learning
styles after mastering the concepts of planning.
Note also that there is a prescriptive quality to this essay; thus, important
value assumptions underlie the reasoning. What is the author concerned about
preserving? Try reverse role-playing. What would someone who disagreed with
this position care about? What are the disadvantages to forcing students to
plan? Your answers to these questions should lead you to the essay's value preference.
For example, can you see how a preference for orderliness over independence
links the reasons to the conclusion?
Avoiding Analysis of Trivial Assumptions
Writers and speakers take for granted, and should take for granted, certain selfevident
things. You will want to devote your energy to evaluating important
assumptions, so we want to warn you about some potential trivial assumptions.
By trivial, we mean an assumption that is self-evident.
You as a reader or listener can assume that the communicator believes his
reasons are true. You may want to attack the reasons as insufficient, but it is trivial
to point out the writer's or speaker's assumption that the reasons are true.
Another type of trivial assumption concerns the reasoning structure. You
may be tempted to state that the writer believes that the reason and conclusion
are logically related. Right—but trivial. What is important is how they are logically
related. It is also trivial to point out that an argument assumes that we
can understand the logic, that we can understand the terminology, or that we
have the appropriate background knowledge.
Avoid spending time on analyzing trivial assumptions. Your search for
assumptions will be most rewarding when you locate hidden, debatable missing
Assumptions and Your Own Writing and Speaking
When you attempt to communicate with an audience, either by writing or
speaking, you will be making numerous assumptions. Communication requires
them. But, once again out of respect for your audience, you should acknowledge
those assumptions, and, where possible, provide a rationale for why you
are making those particular assumptions.
The logic of this approach on your part is to assist the audience in accepting
your argument. You are being open and fair with them. An audience should
appreciate your willingness to present your argument in its fullness.
Assumptions are ideas that, if true, enable us to claim that particular reasons
provide support for a conclusion.
(J) Critical Question: What are the descriptive assumptions?
For each of the three passages, locate important assumptions made by the author.
Remember first to determine the conclusion and the reasons.
Everyone should consider playing poker to win money. It has gained great popularity.
You can see people play on television daily, and there are many opportunities
to play against real people online. This trend is an exciting opportunity
for people everywhere to try and win money. Poker is simple to learn after one
understands the rules and concepts behind the game. It is a game that people of
all ages and experience can play!
Adopted children should have the right to find out who their biological parents
are. They should be able to find out for personal and health reasons. Most children
would want to know what happened to these people and why they were given
up for adoption. Even though this meeting may not be completely the way the
child had imagined it, this interaction could provide a real sense of closure for
adopted children. There are people who believe that it does not matter who the
biological parents are as long as the child has loving parents. It is true that having
a supportive environment is necessary for children, but there will always be nagging questions for these children that will be left unanswered if they are
not able to find out their biological parents. There are also health risks that
can be avoided by allowing a child to find out who their parents are. A lot of
diseases have hereditary links that would be useful for the child and the new
family to know.
Recently, we have lost community members in a large fire. It only seems logical now
mat we start implementing fire safety presentations or courses in our schools. The
last thing we want to happen is for more tragedies to occur, especially in our schools.
The fire safety training will prevent this community from losing any more lives.
Educational programs provide the best way to go if we are to avoid future disasters
of this type.
In presenting assumptions for the following arguments, we will list only some
of the assumptions being made—those which we believe are among the most
CONCLUSION: Everyone should play poker to win money.
REASONS: 1. It is a popular game.
2. People of all ages and experience can play.
In looking at the first reason, there seems to be a missing link between that reason
and the conclusion. The author omits two main assumptions. One, poker is
enjoyable because many people play this game. And second, that "enjoyable"
means profitable. The author needs these two assumptions for him to make the
jump to the idea that we should all join the poker craze.
The second reason should leave the reader wondering whether it makes
sense to assume that because something can happen, it should happen. Yes, we
can all certainly play poker; we can also all start forest fires, but our capacity to
do so is not exactly an endorsement of the activity.
CONCLUSION: Adopted children should be allowed to find their biological parents'
REASON: 1. Knowing ones birth parents can provide many health benefits (SUPPORTING REASONS)
a. Psychological closure can be achieved by finding answer to enduring
b. Able to find out what their biological parents are like.
2. Permits one to assess health risks.
Try reverse role-playing, taking the position of someone who values the
parents' right to privacy.
For the first reason to be true, it must be the case that the child is
bothered by not knowing their biological parentage. Surely this assumption
would be true for some adopted children. Is there data that suggests a widespread
burning desire to know the birth parents? If so, please present the data
so we can move toward agreeing with the argument. There are many reasons
to think that the child may either be satisfied not knowing or may not even be
aware that he is adopted. Also, for the main reason to be enhanced by the
supporting reasons, we would need to assume that meeting the biological
parent would not create sharp new tensions between the individual and the
ff\ CRITICAL QUESTION SUMMARY:
Vjt^ WHY THIS QUESTION IS IMPORTANT
What Are the Descriptive Assumptions?
When you identify descriptive assumptions, you are identifying the link between
a reason and the author's conclusion. If this link is flawed, the reason does not necessarily
lead to the conclusion. Consequently, identifying the descriptive assumptions
allows you to determine whether an author's reasons lead to a conclusion.
You will want to accept a conclusion only when there are good reasons that lead
to the conclusion. Thus, when you determine that the link between the reasons
and conclusion is flawed, you will want to be reluctant to accept the author's