Critical
Thinking: Distinguishing Between
Inferences and Assumptions
To be skilled in critical
thinking is to be able to take one’s thinking apart systematically,
to analyze each part, assess it for quality and then improve it.
The first step in this process is understanding the parts of thinking,
or elements of reasoning.
These elements are: purpose,
question, information, inference, assumption, point of view, concepts,
and implications. They are present in the mind whenever we reason.
To take command of our thinking, we need to formulate both our purpose
and the question at issue clearly. We need to use information in
our thinking that is both relevant to the question we are dealing
with, and accurate. We need to make logical inferences based on
sound assumptions. We need to understand our own point of view and
fully consider other relevant viewpoints. We need to use concepts
justifiably and follow out the implications of decisions we are
considering. (For an elaboration of the Elements of Reasoning, see
a Miniature Guide to the Foundations of Analytic Thinking.)
In this article we focus
on two of the elements of reasoning: inferences and assumptions.
Learning to distinguish inferences from assumptions is an important
intellectual skill. Many confuse the two elements. Let us begin
with a review of the basic meanings:
- Inference: An inference
is a step of the mind, an intellectual act by which one concludes
that something is true in light of something else’s being
true, or seeming to be true. If you come at me with a knife in
your hand, I probably would infer that you mean to do me harm.
Inferences can be accurate or inaccurate, logical or illogical,
justified or unjustified.
- Assumption: An assumption
is something we take for granted or presuppose. Usually it is
something we previously learned and do not question. It is part
of our system of beliefs. We assume our beliefs to be true and
use them to interpret the world about us. If we believe that it
is dangerous to walk late at night in big cities and we are staying
in Chicago, we will infer that it is dangerous to go for a walk
late at night. We take for granted our belief that it is dangerous
to walk late at night in big cities. If our belief is a sound
one, our assumption is sound. If our belief is not sound, our
assumption is not sound. Beliefs, and hence assumptions, can be
unjustified or justified, depending upon whether we do or do not
have good reasons for them. Consider this example: “I heard
a scratch at the door. I got up to let the cat in.” My inference
was based on the assumption (my prior belief) that only the cat
makes that noise, and that he makes it only when he wants to be
let in.
We humans naturally and
regularly use our beliefs as assumptions and make inferences based
on those assumptions. We must do so to make sense of where we are,
what we are about, and what is happening. Assumptions and inferences
permeate our lives precisely because we cannot act without them.
We make judgments, form interpretations, and come to conclusions
based on the beliefs we have formed.
If you put humans in
any situation, they start to give it some meaning or other. People
automatically make inferences to gain a basis for understanding
and action. So quickly and automatically do we make inferences that
we do not, without training, notice them as inferences. We see dark
clouds and infer rain. We hear the door slam and infer that someone
has arrived. We see a frowning face and infer that the person is
upset. If our friend is late, we infer that she is being inconsiderate.
We meet a tall guy and infer that he is good at basketball, an Asian
and infer that she will be good at math. We read a book, and interpret
what the various sentences and paragraphs-indeed what the whole
book-is saying. We listen to what people say and make a series of
inferences as to what they mean.
As we write, we make
inferences as to what readers will make of what we are writing.
We make inferences as to the clarity of what we are saying, what
requires further explanation, what has to be exemplified or illustrated,
and what does not. Many of our inferences are justified and reasonable,
but some are not.
As always, an important
part of critical thinking is the art of bringing what is subconscious
in our thought to the level of conscious realization. This includes
the recognition that our experiences are shaped by the inferences
we make during those experiences. It enables us to separate our
experiences into two categories: the raw data of our experience
in contrast with our interpretations of those data, or the inferences
we are making about them. Eventually we need to realize that the
inferences we make are heavily influenced by our point of view and
the assumptions we have made about people and situations. This puts
us in the position of being able to broaden the scope of our outlook,
to see situations from more than one point of view, and hence to
become more open-minded.
Often different people
make different inferences because they bring to situations different
viewpoints. They see the data differently. To put it another way,
they make different assumptions about what they see. For example,
if two people see a man lying in a gutter, one might infer, “There’s
a drunken bum.” The other might infer, “There’s
a man in need of help.” These inferences are based on different
assumptions about the conditions under which people end up in gutters.
Moreover, these assumptions are connected to each person’s
viewpoint about people. The first person assumes, “Only drunks
are to be found in gutters.” The second person assumes, “People
lying in the gutter are in need of help.”
The first person may
have developed the point of view that people are fundamentally responsible
for what happens to them and ought to be able to care for themselves.
The second may have developed the point of view that the problems
people have are often caused by forces and events beyond their control.
The reasoning of these two people, in terms of their inferences
and assumptions, could be characterized in the following way:
Person One Person Two
Situation: A man is lying in the gutter. Situation: A man is lying
in the gutter.
Inference: That man’s a bum. Inference: That man is in need
of help.
Assumption: Only bums lie in gutters. Assumption: Anyone lying in
the gutter is in need of
help.
Critical thinkers notice
the inferences they are making, the assumptions upon which they
are basing those inferences, and the point of view about the world
they are developing. To develop these skills, students need practice
in noticing their inferences and then figuring the assumptions that
lead to them.
As students become aware
of the inferences they make and the assumptions that underlie those
inferences, they begin to gain command over their thinking. Because
all human thinking is inferential in nature, command of thinking
depends on command of the inferences embedded in it and thus of
the assumptions that underlie it. Consider the way in which we plan
and think our way through everyday events. We think of ourselves
as preparing for breakfast, eating our breakfast, getting ready
for class, arriving on time, leading class discussions, grading
student papers, making plans for lunch, paying bills, engaging in
an intellectual discussion, and so on. We can do none of these things
without interpreting our actions, giving them meanings, making inferences
about what is happening.
This is to say that we
must choose among a variety of possible meanings. For example, am
I “relaxing” or “wasting time?” Am I being
“determined” or “stubborn?” Am I “joining”
a conversation or “butting in?” Is someone “laughing
with me” or “laughing at me?” Am I “helping
a friend” or “being taken advantage of?” Every
time we interpret our actions, every time we give them a meaning,
we are making one or more inferences on the basis of one or more
assumptions.
As humans, we continually
make assumptions about ourselves, our jobs, our mates, our students,
our children, the world in general. We take some things for granted
simply because we can’t question everything. Sometimes we
take the wrong things for granted. For example, I run off to the
store (assuming that I have enough money with me) and arrive to
find that I have left my money at home. I assume that I have enough
gas in the car only to find that I have run out of gas. I assume
that an item marked down in price is a good buy only to find that
it was marked up before it was marked down. I assume that it will
not, or that it will, rain. I assume that my car will start when
I turn the key and press the gas pedal. I assume that I mean well
in my dealings with others.
Humans make hundreds
of assumptions without knowing it---without thinking about it. Many
assumptions are sound and justifiable. Many, however, are not. The
question then becomes: “How can students begin to recognize
the inferences they are making, the assumptions on which they are
basing those inferences, and the point of view, the perspective
on the world that they are forming?”
There are many ways to
foster student awareness of inferences and assumptions. For one
thing, all disciplined subject-matter thinking requires that students
learn to make accurate assumptions about the content they are studying
and become practiced in making justifiable inferences within that
content. As examples: In doing math, students make mathematical
inferences based on their mathematical assumptions. In doing science,
they make scientific inferences based on their scientific assumptions.
In constructing historical accounts, they make historical inferences
based on their historical assumptions. In each case, the assumptions
students make depend on their understanding of fundamental concepts
and principles.
As a matter of daily
practice, then, we can help students begin to notice the inferences
they are making within the content we teach. We can help them identify
inferences made by authors of a textbook, or of an article we give
them. Once they have identified these inferences, we can ask them
to figure out the assumptions that led to those inferences. When
we give them routine practice in identifying inferences and assumptions,
they begin to see that inferences will be illogical when the assumptions
that lead to them are not justifiable. They begin to see that whenever
they make an inference, there are other (perhaps more logical) inferences
they could have made. They begin to see high quality inferences
as coming from good reasoning.
We can also help students
think about the inferences they make in daily situations, and the
assumptions that lead to those inferences. As they become skilled
in identifying their inferences and assumptions, they are in a better
position to question the extent to which any of their assumptions
is justified. They can begin to ask questions, for example, like:
Am I justified in assuming that everyone eats lunch at 12:00 noon?
Am I justified in assuming that it usually rains when there are
black clouds in the sky? Am I justified in assuming that bumps on
the head are only caused by blows?
The point is that we
all make many assumptions as we go about our daily life and we ought
to be able to recognize and question them. As students develop these
critical intuitions, they increasingly notice their inferences and
those of others. They increasingly notice what they and others are
taking for granted. They increasingly notice how their point of
view shapes their experiences.
This article was adapted
from the book, Critical
Thinking: Tools for Taking Charge of Your Learning and Your Life,
by Richard Paul and Linda Elder.
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