The Nature and Logic of Science
Empirical Knowledge is based on:
• Observations
• Sensory data
• Facts
• Repeated observations
• Confirmed by consensus
• Conceptualizations
• Abstract statements that relate facts and observations with one
another
Types of Conceptualizations
• Generalization
• A statement that applies to a large group of objects or
phenomena
• Hypothesis
• A tentative explanation for phenomena
• Seeks to explain cause and effect
• Theory
• An explanatory hypothesis that has been well tested and
supported by empirical data
THE CELL THEORY
• In the late 1660s, Robert Hooke
and Anton van Leeuwenhoek were
the first to observe cells.
WHERE DO CELLS COME FROM?
• The cell theory states that all
organisms are made of cells and all
cells come from preexisting cells.
•Louis Pasteur showed that cells
arise from cells and not by
spontaneous generation.
INFERENCE AND PREDICTIONS:
• Because all cells come from
preexisting cells, single-celled
organisms in a population are
related to a single common
ancestor, and all cells in a
multicellular organism also descend
from a single ancestral cell.
THE THEORY OF EVOLUTION
BY NATURAL SELECTION
• In 1858, Darwin and Wallace
proposed that all species are
related by descent from a common
ancestor.
WHAT IS EVOLUTION?
• Species change over time and are
related to one another. Natural
selection explains how this occurs.
WHAT IS NATURAL SELECTION?
• Individuals of the same species
living in the same area at the same
time constitute a population.
WHAT IS NATURAL SELECTION?
•In natural selection, the
population’s characteristics will
change over time as the individuals
with the favorable traits increase in
frequency.
WHAT IS NATURAL SELECTION?
•In artificial selection, individuals
in a population are selected for
mating based on particular traits.
Repeating this process over
generations results in a population
with altered characteristics.
The Logic of Science
• Induction
• A general statement based upon a set of observations (a hypothesis)
• Deduction
• A predictive statement that follows logically from acceptance of the
hypothesis (a test)
• If….., then….. Reasoning
• Biologists ask questions, generate hypotheses to answer them, and
design experiments that test the predictions made by competing
hypotheses.
Hypothesis Testing –
The Truth Table
Hypothesis
True
Conclusion
(prediction)
True
False
True or false
• Therefore, hypotheses should be falsifiable
• Science does not prove!!!
DOING BIOLOGY
• Biologists test ideas about how the
natural world works by evaluating the
predictions made by alternative
hypotheses. Carefully designed
experiments are an important tool for
hypothesis testing.
WHY DO GIRAFFES HAVE LONG
NECKS? AN INTRODUCTION TO
HYPOTHESIS TESTING
• Simmons and Scheepers tested the
food competition hypothesis that
giraffes evolved long necks by
natural selection because those with
long necks reach food unavailable to
others.
The Food Competition Experiment Predictions
• Neck length is variable
• Neck length is heritable
• Giraffes feed high in trees to avoid competition
from other animals
THE FOOD COMPETITION HYPOTHESIS:
PREDICTION AND TESTS
• One of the three predictions of
the food competition hypothesis,
that giraffes feed high in trees,
does not hold true; thus, there may
be better alternative hypotheses to
explain neck length in giraffes.
THE SEXUAL COMPETITION HYPOTHESIS:
PREDICTIONS AND TESTS
• An alternative hypothesis is that
giraffes evolved long necks
because males with longer necks
win more fights than shorternecked giraffes and can then father
more offspring. Data support this
hypothesis.
Paradigm
The Structure of Scientific Revolutions – Kuhn (1970)
• A broad collection of ideas, assumptions, and ideas that guide
research in any field.
• Resistant to change
• Paradigm shift occurs when contrary evidence reaches a “critical”
level
• Paradigm shift may be large or small
Critical Realism
• Realism is a philosophical position stating that there is a
fundamental truth or reality to all things.
• Critical indicates that our understanding of that truth is open to
question or reinterpretation.
• This means that our current view of the world is always
provisional.
• The scientific method is a critically realistic approach to
understanding the natural world.
• Can critical realism also be applied to religion?
The Structure of Science
Concepts
Theories
Imagination
Theories
influence
observation
Analogies
Models
Observation
Data
The Structure of Religion
Concepts
Beliefs
Imagination
Beliefs influence
experience and
interpretation
Analogies
Models
Religious experience
Story and ritual
IGNATIAN PEDAGOGY
• Based upon the Spiritual Excercises
of St. Ignatius of Loyola
• Strategies for student engagement
•Hallmark of Jesuit higher education
IGNATIAN PEDAGOGY
•Context
•Experiences
•Reflection
•Action
•Evaluation
Ignatian Pedagogical Cycle
Context
Experience
Reflection
Evaluation
Action
The Scientific Method
Paradigms
Observation
Hypothesis
Analysis
(cause/effect)
Experiment
Data