Deductive reasoning

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Deductive reasoning
Science, People, and The Environment
Anthony O. Oloni, MD, MPH, CPHI
Environmental Science
The systematic, scientific study of
our environment as well as our role
in it.
The study of ecology:
The branch of biology concerned with
the relations between organisms and
their environment
Environmental Science
Environmental science is the science
of the interactions between the
physical, chemical, and biological
components of the environment,
including their effects on all types of
organisms but more often refers to
human impact on the environment.
Environmental sustainability is an
important concern of environmental
science. Why?
Examples of environmental
Environmental Sustainability!
So, what is environmental
Environmental sustainability
Long-term maintenance of ecosystem
components and functions for future
The assessment that a projects outputs can
be produced without permanent and
unacceptable change in the natural
environment on which it and other economic
activities depend, over the life of the
What is environmental Sustainability?
Meeting the needs of the present without
compromising the ability of future
generations to meet their needs.
e.g. Keeping population densities below the
carrying capacity of a region, facilitating the
renewal of renewable resources, conserving
and establishing priorities for the use of nonrenewable resources
Keeping environmental impact below the
level required to allow affected systems to
recover and continue to evolve
Environmental Health Risk Assessment
As characterized by the WHO
Identify of the environmental hazard
Hazard and the effects of the hazard
Dose-Response Assessment
Relationship between the dose and
health effect in humans
Environmental Risk Assessment
Exposure Assessment
What exposures are currently
anticipated under different conditions.
Risk Characterization
Estimation of the incidence of the adverse
effect in the given population
Environmental Risk Assessment
Risk Management (Risk Control)
Development, evaluation and
implementation of regulatory options
aimed at risk reduction and control
Scientific Method
The scientific method is the process by
which scientists, collectively and over time,
endeavor to construct an accurate (that is,
reliable, consistent and non-arbitrary)
representation of the world.
Scientific Method
The step by step process by which
scientists investigate hypotheses using
Is the testing of scientific principles and
procedures for the systematic pursuit of
knowledge involving the recognition and
formulation of a problem, the collection of
data through observation and experiment,
and the formulation and testing of
Scientific Method
A proposal intended to explain certain
presumed facts or observations
 A tentative theory about the natural world
 A concept that is not yet verified but that if
true would explain certain facts or phenomena
 A scientific hypothesis that survives
experimental testing becomes a scientific
theory"; "he proposed a fresh theory of alkalis
that later was accepted in chemical practices"
Very educated guess: a message expressing
an opinion based on incomplete evidence
The scientific method steps
A proposal intended to explain certain facts or
A tentative theory about the natural world; a
concept that is not yet verified but that if true
would explain certain facts or phenomena;
“A scientific hypothesis that survives
experimental testing becomes a scientific
theory"; "he proposed a fresh theory of alkalis
that later was accepted in chemical practices"
Scientific Method
A process that is the basis for
scientific inquiry. The scientific
method follows a series of steps:
(1) Identify a problem you would like to
solve (i.e. does water increase its
temperature when turning into steam?)
(2) Formulate a hypothesis
(3) Test the hypothesis
(4) Collect and analyze the data
(5) Make conclusions.
The scientific method steps
We spend our lifetimes being observers.
However, most of these observations are
different from the ones which characterize
scientific research.
One of the early challenges in learning to be a
psychologist is to distinguish between the
casual observations you make as part of your
everyday experience and the observations
which can supply good behavioral data for a
research project.
The scientific method steps
Data Collection
The process of gathering and
measuring information on variables of
interest in an established systematic
fashion that enables one to answer
stated research questions, test
hypotheses, and evaluate outcomes.
The scientific method steps
An investigation of the component parts of a
whole and their relations in making up the whole.
The process of explaining an entity or idea by
examining it in terms of its various parts (e.g., a
statistical technique for defining and segregating
the causes of variability affecting a set of
The scientific method steps
A position or opinion or judgment
reached after consideration; "a decision
unfavorable to the opposition"; "his
conclusion took the evidence into
account"; "satisfied with the panel's
Scientific Method
The procedure scientists follow to
understand the natural world:
The observation of phenomena or the
results of experiments;
The formulation of hypotheses that
describe these phenomena and that
are consistent with the body of
knowledge available;
Scientific Method
(3) The testing of these hypotheses by
noting whether or not they adequately
predict and describe new phenomena
or the results of new experiments;
(4) The modification or rejection of
hypotheses that are not confirmed by
The scientific method steps
the act of conducting a controlled test
or investigation
a venture at something new or
different; "as an experiment he decided
to grow a beard"
Scientific Method
Deductive Reasoning.
Reasoning based on facts.
Combined with empiricism to create
scientific method.
Drawing conclusions from
observations of the natural world by
means of logical reasoning.
Deductive Reasoning
Examples of deductive reasoning may be both
subtle and time-saving. For example, Be careful
of that wasp: it might sting. is based on the logic
that wasps as a class have stingers; therefore
each individual wasp will have a stinger.
This conclusion is freeing in that we do not have
to examine each and every wasp we ever
encounter to ascertain what characteristics it may
have. Because of the validity of deductive
reasoning, we may make an assumption that is
both useful and efficient.
Deductive reasoning
Deductive reasoning is the kind of reasoning in
which the conclusion is necessitated by, or
reached from, previously known facts (the
premises). If the premises are true, the
conclusion must be true. This is distinguished
from adductive and inductive reasoning, where
the premises may predict a high probability of the
conclusion, but do not ensure that the conclusion
is true.
Deductive reasoning may also be defined as
inference in which the conclusion is of no greater
generality than the premises or inference in which
the conclusion is just as certain as the premises.
Deductive reasoning
Deductive reasoning, or deduction, starts
with a general case and deduces specific
Deduction is used by scientists who take a
general scientific law and apply it to a
certain case.
Sherlock Holmes used deduction when he
took some general indicators and deduced
the specific details of a rather knotty
Deductive Reasoning
Deductive Reasoning is the process of
reasoning from general principles to
other general principles or specific
examples. For example, a reasoner,
knowing that all crows are black (a
general fact about crows) can conclude
that my pet crow (a specific example) is
black. Similarly, the same reasoner,
knowing that crows are birds, can
conclude that some birds are black
(another general principle regarding
Deductive Reasoning
Much of the study of formal logic has involved
mechanistic or algorithmic methods both for the
representation of these general principles and for
methods of making inferences from these principles
that are guaranteed to be correct. When properly
performed, deductive logic is sound, which is to say
that if the premises of the argument are true, the
conclusion is guaranteed to be true (or alternatively, if
the conclusion is false, at least one of the premises
must have been false; if my pet is white, then either I
am mistaken in thinking it to be a crow, or not all
crows are white).
It should be noted that deductive reasoning can never
generate "new" truths, therefore all genuine
experimentation or empirical research will of necessity
involve elements of inductive reasoning.
Inductive Reasoning
The process of thinking in which a
conclusion is made based on
Drawing a general conclusion based on
a limited set of observations.
Inductive Reasoning
Inductive Reasoning is used when a sequence
of individual pieces of information is generalized
into a conclusion that relates to those pieces of
information (e.g. After several cakes baked in the
same cake pan came out burned, Carl concluded
that if he bakes a cake in that particular cake pan
it will probably come out burned).
On the THEA test, an inductive reasoning question
will take the form of a sequence of numbers or
figures that exhibit a trend (increasing,
decreasing, alternating, or a combination of
these). By recognizing the trend, you must draw a
conclusion about the next (or missing) number or
figure in the sequence.
Inductive reasoning
Induction or inductive reasoning,
sometimes called inductive logic, is the
process of reasoning in which the
premises of an argument are believed to
support the conclusion but do not ensure
it. It is used to ascribe properties or
relations to types based on tokens (i.e.,
on one or a small number of observations
or experiences); or to formulate laws
based on limited observations of recurring
phenomenal patterns.
"Induction is a major kind of reasoning
process in which a conclusion is drawn from
particular cases. It is usually contrasted
with deduction, the reasoning process in
which the conclusion logically follows from
the premises, and in which the conclusion
has to be true if the premises are true. In
inductive reasoning, on the contrary, there
is no logical movement from premises to
conclusion. The premises constitute good
reasons for accepting the conclusion. The
premises in inductive reasoning are usually
based on facts or observations.
There is always a possibility, though, that
the premises may be true while the
conclusion is false, since there is not
necessarily a logical relationship between
premises and conclusion." From: Grolier's
1994 Multimedia Encyclopedia
Inductive reasoning is used when
generating hypotheses, formulating
theories and discovering relationships, and
is essential for scientific discovery.
Inductive reasoning: (1) Conclusion
based on several past observations (2)
Conclusion is probably true, but not
necessarily true
Deductive Reasoning: (1) Conclusion
based on accepted statements
(definitions, postulates, previous
theorems, corollaries, and given
information) (2) Conclusion must be true
if hypotheses are true
Marginal Cost of Pollution
A marginal cost is the additional
cost associated with one more unit
of something. Two examples of
marginal costs associated with
pollution are the effects of pollution
on human health and on organisms
in the natural environment.
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