Scientific Knowledge
The nature of knowledge is a subject contemplated by philosophers for a very long time.
The main difference between scientific and other types of knowledge is that scientific
knowledge must be testable both logically and experimentally.
Studies of knowledge in science indicate that knowledge may be classified into two
major categories—empirical (observable) or theoretical (non-observable).
Table 1: Characteristics of Empirical and Theoretical Knowledge
Scientific Knowledge
Characteristics
Empirical
 based on observations and experiment
 used to describe and predict phenomenon
 communicated by qualitative and quantitative
descriptions, empirical hypotheses, empirical definitions,
generalizations and scientific laws*
Theoretical
 based on ideas/concepts of the unseen
 used to describe, predict and explain phenomenon
 communicated by qualitative and quantitative
descriptions, theoretical hypotheses, theoretical
definitions, and theories*
* Some branches of science, like biology, sometimes use laws and theories in a different way.
This is discussed in more detail in the sections about empirical and theoretical processes.
In general, the methodology of any branch of science can be described as the
collection and analysis of observations to find valid empirical concepts, and the
development and testing of theories to explain this empirical knowledge. Except for a few
modern examples, the empirical work generally starts first and the theoretical work
follows at some later time. Some examples from the history of chemistry are provided in
Table 2. The dates in Table 2 come from Asimov’s Biographical Encyclopedia of Science
and Technology and Brock’s The Chemical Tree.
Table 2: Some Empirical and Theoretical Concepts in the History of Chemistry
Empirical Concept
conservation of mass (Lavoisier, 1770s)
conservation of momentum (Wallis, 1668)
gas laws (Boyle, 1662 & Charles, 1787)
Faraday’s laws (Faraday, 1832)
periodic law (Mendeleev, 1869)
stoichiometry (Richter, 1792)
definite composition (Proust, 1799)
multiple proportions (Berthollet, 1799+)
rate of reactions (van’t Hoff, 1884)
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Theoretical Concept
conservation of atoms (Dalton, 1805)
particle repulsion (Van der Waals, 1873)
kinetic molecular theory (Maxwell, ~1860)
electrochemical theory (Debye, 1923)
Bohr model of atom (1913)
mole ratio (after Avogadro, >1856)
atomic theory (Dalton, 1805)
valence theory (Pauling, 1928+)
particle kinetics (Hughes & Ingold, 1933)
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equilibrium (Berthollet, 1798)
Le Chatelier’s principle (1888)
neutralization (Ostwald, 1877)
electricity (Franklin, 1752)
line spectra (Kirchoff, 1859; Balmer, 1885)
law of gravitation (Newton, 1666 & 1687)
equilibrium (Gibbs, 1890s)
equilibrium & kinetics (Gibbs, 1890s)
H+(aq) of Arrhenius (1884)
electron flow (Thomson, 1897)
quantization of energy (Bohr, 1913)
theory of gravitation (still coming)
Note that the concepts listed in Table 2 are created by different scientists. One could
describe the scientists who created the empirical concepts as empiricists (experimental
scientists who emphasize laboratory work). The scientists who create theoretical
knowledge may be called theoreticians. However, classification schemes like this are
created by human beings to help organize our knowledge—it is not likely that any one
scientist can be classified as either/or, just having a different degree of empiricism at any
point in time in his/her work.
Empirical and Theoretical Ways of Knowing
Scientific ways of knowing may also be classified as empirical and theoretical. An
empirical way of knowing is characterized by a dependence on experience and
experiment, while a theoretical way of knowing is characterized by thinking about
entities and actions that are not visible to the human eye. The history of science can be
seen as involving parallel streams of work—empirical and theoretical. Every situation is
unique, for example, the empirical study of a phenomenon may be decades, centuries or
millennia ahead of theoretical work or the empirical and theoretical work may be feeding
off one another on an ongoing basis—each making advances in knowledge that is
communicated to the other. Modern scientific work is increasingly teamwork, with
empiricists and theoreticians working closely together, along with their counterparts from
related disciplines (e.g., chemistry, physics and biology).
Table 3: Empirical and Theoretical Scientific Work
Empirical stream of work
(typically ahead)
empirical descriptions based on
observations and communicated as
 evidence
 tables
 graphs
empirical concepts (from the evidence)
 empirical definitions
 empirical hypotheses
 empirical generalizations
 empirical models
 scientific laws
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Theoretical stream of work
(typical behind, in time)
theoretical concepts based on ideas about
the invisible (to explain the evidence)
 theoretical definitions
 theoretical hypotheses
 theoretical generalizations
 theoretical models
theoretical descriptions (from the concepts)
, for example,
 according to the Bohr model of the
atom, a carbon atom has four valence
electrons
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